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Container Soils - Water Movement and Retention 8/26/21

tapla
11 months ago
last modified: 11 months ago

Hello! This post has 3 pages. Houzz's format won't allow me to post the thread in it's entirety, so the thread will continue in the 2 text boxes subsequent to my OP. It's necessary to repost the thread from time to time because after a given number of replies, part 2 and/or 3 get archived and are difficult to find. I'll try to be better about reposting as soon as the number of posts reaches that point.

I want to thank all the growers and good people who have participated and been so supportive of the thread over the years. Their contributions are one of the main reasons viewers continue to find interest in it, so thank you very much! If you find value in the information I have set down in this post and feel there is anything pertaining to the topic that should be added or explored in more detail, please contribute your suggestions. My goal is to offer information that allows you to avoid an ongoing battle with your medium for control of your plants' vitality, information that will help you increase the reward you get in return for your efforts.

I started this thread about 15 years ago, in March of '05. So far, it has reached the maximum number of posts GW allowed to a single thread twenty two times, which is much more attention than I ever imagined it would garner. Currently, there have been just over 6,200 posts to the singular topic. I have reposted it in no small part because it has been great fun, and a wonderful catalyst in the forging of new friendships and in increasing my list of acquaintances with similar growing interests. The forum and email exchanges that so often stem from the subject matter are in themselves enough to make me hope the subject continues to pique interest, and the exchanges provide helpful information. Most of the motivation to post this thread another time comes from the reinforcement of hundreds of participants over the years that strongly suggests the information provided in good-spirited collective exchange has made a significant difference in the quality of their growing experience. Thank you for taking the time to examine this topic - I hope that any/all who read it take at least something interesting and helpful from it. I know it's long, and grows a little longer each time it's reposted. My hope is that you find it worth the read, and the time you invest results in a significantly improved growing experience. Since there are many questions about soils appropriate for use in containers, I'll post basic mix recipes later, in case any would like to try them. Also, you will find I use the terms medium/ media and soil/ soils interchangeably.

As you eye the length of this post, one thing you might ask yourself is, "Why the interest and all this talk about soils and water retention?" In all honesty, soils obscure the reason we talk about them - they hide the roots and the roots' state of vitality. Vitality is not the same as vigor. Vigor is a genetic factor, something the plant is endowed with because of how it was programmed by Mother Nature. It is also something we have no sway over. Vitality, on the other hand, is dynamic and variable, essentially a measure of how well a plant is/ has been able to deal with the cultural hand it has been dealt by the grower. Vitality is something you have much, perhaps nearly total control over. The visual signals we get from the parts of the plant we CAN see allow us to take measure of the condition of the roots and the plant's overall vitality. Soil choice and watering habits, have a very significant impact on root health. As you read, keep in mind that good root health and root function are an essential PREREQUISITE to a healthy plant. We cannot expect to grow healthy plants w/o a healthy root system - it is impossible; which brings us full circle to why we discuss soils.

Poor root health is responsible for a very high percentage of the ills that befall plants, and the reasons people flock to the forums seeking remediation for widely varying issues. Poor root health means a reduction in vitality, which leaves the plant looking shabby while compromising its ability to defend itself against insects and diseases. So, let's talk about some things we can implement that should go a very long way toward providing you with the ability to consistently keep the root systems of your plants happy.

Before we get started, I'd like to mention that I wrote a reply and posted it to a thread some time ago, and I think it is well worth considering. It not only sets a minimum standard for what constitutes a 'GOOD' container medium, but also points to the fact that not all growers look at container media from the same perspective, which is why growers so often disagree on what makes a medium 'good, bad, or somewhere in between. I hope you find it thought provoking:

IS 'X' A GOOD SOIL?

I think any discussion on this topic must largely center around the word "GOOD", and we can broaden the term 'good' so it also includes 'quality' or 'suitable', as in "Is X a quality or suitable medium?" How do we determine if medium A or medium B is a good one? And before we do that, we had better decide if we are going to look at it from the plant's perspective or from the grower's perspective, because often there is a considerable amount of conflict to be found in the overlap - so much so that one can often be mutually exclusive of the other.

We can imagine that grower A might not be happy or satisfied unless knows he is squeezing every bit of potential from his plants, and grower Z might not be happy or content unless he can water his plants before leaving on a 2-week jaunt and still have a weeks worth of not-having-to-water when (s)he returns. Everyone else is somewhere between A and Z; with B, D, F, H, J, L, N, P, R, T, V, X, and Y either unaware of how much difference medium choice can make, or, they understand but don't care.

I said all that to illustrate the large measure of futility in trying to establish any sort of standard as to what makes a medium 'good' from the individual grower's perspective; but let's change our focus from the pointless to the possible. We're really only interested in the comparative degrees of 'good' and 'better' here. It would be presumptive to label any medium "best", though 'best I've found' or 'best I've used' CAN sometimes be useful for comparative purposes, but that's a very subjective judgment. Let's tackle 'good', then move on to 'better', and finally see what we can do about qualifying these descriptors so they can apply to all growers.

I would like to think that everyone would prefer to use a medium that can be described as 'good' from the plant's perspective. How do we determine what a plant wants? Surprisingly, we can use %s established by truly scientific studies that are widely accepted in the greenhouse and nursery trades to determine if a medium is good or not good - from the plant's perspective, that is. Rather than use confusing numbers that mean nothing to the hobby grower, I can suggest that our standard for a good should be, at a minimum, that you can water properly. This means at any time during the growth cycle you should be able to water your plantings to beyond the point of saturation (so excess water is draining from the pot) without the fear of root rot or compromised root function due to (take your pick) an excessive volume of water or too little air in the root zone.

I think it is very reasonable to withhold the comparative adjective, 'GOOD', from media that can't be watered properly without compromising root function, or worse, suffering disease from one of the fungaluglies that cause root rot. I also think anyone wishing to make a case from the plant's perspective that a medium which can't be watered to beyond saturation w/o compromising root health can be called 'good', is fighting uphill against logic.

So I contend that 'GOOD' soils are those we can water correctly; that is to say, we can flush the medium when we water without concern we would be compromising root health/function due to long term retention of excess water. If you ask yourself, "Can I water correctly if I use this medium?" and the answer is 'NO' .... it's not a good choice .... for the reasons stated above. Can you water correctly using most of the bagged bagged potting media readily available? 'NO', not without work-arounds in place, and we can talk about those.

What about 'BETTER'? Can we determine what might make a better medium? Yes, we can. If we start with a medium which meets the minimum standard of 'good', and improve either the physical or chemical properties of it, or make it last longer structurally, then we have 'better'. Even if we cannot agree on how low we wish to set the bar for what constitutes 'good', we should be able to agree any medium that reduces excess water retention and increases aeration ensures better potential for optimal root health than media which only meet some one's individual and arbitrary standard of 'good'.

All the plants we grow, unless grown from seed, have the genetic potential to become beautiful specimens. It's easy to see the absolute truth in the idea that if you give a plant everything it needs to prosper it will flourish. The better we are at it, the better our plants will grow. But we all know it's not that easy. Lifetimes are spent in careful study, trying to determine just exactly what it is that plants want and need to make them grow best.

Since this is a discussion, let's examine what the plant wants from its soil. It wants a soil in which we have endeavored to provide in available form, all the essential nutrients, in the ratio in at which the plant uses them, at a concentration high enough to prevent deficiencies yet low enough to make it easy to take up water (and the nutrients dissolved in the water). First and foremost, though, the plant wants a container medium that is evenly damp, never wet or soggy. Giving a plant what it wants to flourish and grow doesn't include a medium half saturated for a week before aeration returns to the entire mass, even if we only water in small sips. Plants might do 'ok' in some water-retentive soils if the grower is highly skilled, but in order to actually flourish as plants are genetically programmed to do, they would need to be unencumbered by media which do not remain wet/ soggy for extended periods.

What defines our proficiency as growers is our ability to identify and reduce the effects of limiting factors, or by eliminating those limiting factors entirely; in other words, by addressing those influences inhibiting the plant from reaching its genetic potential. Even if we are able to provide every other factor that influences plant growth/ vitality perfectly, it could not make up for a substandard medium. For a plant to realize its full genetic potential, every factor has to be perfect, including the medium. Of course, we'll never manage to get to that point, but the good news is, as we get closer and closer, our plants get better and better; and almost certainly, we'll find our growing experience more rewarding.

In my travels, I've discovered it almost always ends up being that one little factor that we willingly or unwittingly overlooked that limits us in our abilities, and our plants in their potential. Mother nature always sides with the hidden flaw.

Food for thought:

A 2-bit plant in a $10 has a future full of potential, where a $10 plant in a 2-bit has only a future filled with limitations. ~ Al

CONTAINER MEDIA – and WATER RETENTION

This is where we get to the meat of the subject. As container gardeners, our first priority should be to ensure the media we use provide adequate aeration for the intended life of the planting, or in the case of perennial material (trees, shrubs, garden perennials), from repot to repot. Aeration/drainage is arguably the most important consideration in any container planting. The soil is the foundation all container plantings are built on, and aeration is the very cornerstone of that foundation. Since aeration and drainage are inversely linked to soil particle size, it makes good sense to try to find and use (or make, in the case of 'media/ soils') soils or primary components with particles larger than peat/ compost/ coir/sand/ top or other traditionally 'fine' ingredients.. Durability and stability of soil components so they contribute to the retention of soil structure for extended periods is also extremely important. Pine and some other types of conifer bark fit the bill nicely, but I'll talk more about various components later.

What I will write will also hit heavily against the futility in using a “drainage layer” of coarse materials in attempt to improve drainage. It just doesn't work. All drainage layers do is reduce the total volume of medium available for root colonization. A wick can be employed to remove water from the saturated layer of medium at the container bottom, but a drainage layer is not effective. A wick can be made to work in reverse of 'self-watering' pots.




CONSIDER THIS IF YOU WILL:

If we agree we should avoid ingredients that are phytotoxic (toxic to plants) our primary consideration when building/buying a container medium should be the medium's structure and its structural stability. Size of the particles that make up a medium, the ratio at which they are combined, and the long term durability (resistance to breaking down into smaller and smaller particles) plays a primary role in determining whether a medium is suited or unsuited to the application. The medium fills only a few needs in container culture. Among them are: Anchorage - a place for roots to extend, securing the plant and preventing it from toppling. Nutrient Retention - it must retain a nutrient supply in available form sufficient to sustain plant systems. Gas Exchange - it must be amply porous to allow air to move through the root system and gasses, which are a by-product of decomposition, to escape. Water - it must retain water enough in liquid and/or vapor form to sustain plants between waterings. Air - it must contain a volume of air sufficient to ensure that root function/metabolism/growth is not impaired. This is extremely important and the primary reason that heavy, water-retentive media are so limiting. Most plants can be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement/ retention of water in container media.

There are two forces that cause water to remain in or move through soils – one is gravity, the other capillary action. Gravity needs little explanation because all things are pulled toward the center of the earth. For this writing I would like to note: Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like particles and the sides of the pot; it is the reason water can stick to the inside of your vertical shower door. Cohesion is the tendency for water to stick to itself. Cohesion is why we often find water in droplet form – because cohesion is at times stronger than adhesion; in other words, water's bond to itself can be stronger than the bond to the object it might be in contact with. Capillary action is adhesion + cohesion, forces in evidence when we dip a paper towel in water. The water will soak into the towel and rise several inches above the surface of the water. It will not drain back into the source, and it will stop rising when the force of gravity is equal to the capillary attraction of the fibers in the paper.

There will be a naturally occurring "perched water table" (PWT), also referred to as a 'perched water column' in containers when soil particle size is under about .100 (a little smaller than 1/8) inch. It is created whenever the capillary pull of the medium (remember how the water climbed up the paper towel and defied gravity) surpasses the Gravitational Flow Potential GFP (weight of the water column in the pot); therefore, the water does not drain, it is said to be 'perched'. The smaller the size of the particles in a medium, the more surface area there is for water to 'stick to', so the greater the capillarity and the greater the height of the PWT. Perched water can be tightly held in heavy (comprised of small particles) soils where it perches (think of a bird on a perch) just above the container bottom where it will not drain; or, it can perch in a layer of heavy medium on top of a coarse drainage layer, where again it will not drain. It is water that resists gravity whenever the force of capillarity is stronger (when particle size is too small) and will not allow the PW to drain from the portion of the pot it occupies. It can evaporate or be used by the plant, but ambient physical forces will not allow it to drain naturally.

Imagine we have five cylinders of varying heights, shapes, and diameters, each with drain holes. If we fill them all with the same medium mixture, then saturate the medium, the PWT will be exactly the same height in all the containers.


This saturated area of the container is where roots initially seldom penetrate and where root problems frequently begin due to a lack of aeration and the production of noxious gasses which cannot escape waterlogged media. Water and nutrient uptake are also compromised by lack of air in the rhizosphere (root zone). Keeping in mind the fact that the PWT height is dependent on soil particle size and has nothing to do with height or shape of the container, we can draw the conclusion that: If using a medium that supports perched water, taller growing containers will always have a higher percentage of unsaturated than squat containers when using the same medium. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding above the PWT. From this, we could make a good case that taller containers are easier to grow in.

~ continued in the text box below ~

Comments (56)

  • a1an
    10 months ago
    last modified: 10 months ago

    Shall someone refresh my memory. How much N tieup occurs as the bark breaks down


    tapla thanked a1an
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  • tapla
    Original Author
    10 months ago

    Bark, and especially conifer bark, breaks down very slowly by virtue of its inclusion of significant amounts of both suberin, a naturally occurring polyester biopolymer, and lignin, another biopolymer. Both compounds are hydrophobic (repel water), which plays a major part in why hydrocarbon chains of both materials are so resistant to cleavage by fungi and herbivorous organisms of all sizes, a characteristic which significantly limits N immobilization in media based in large part on conifer bark.

    While N immobilization does occur, especially when using fresh (uncomposted bark), I have never found it to be a problem unless I drop the ball and allow intervals between fertilizer applications to become a limiting factor. IOW, if you keep up with your plants' N needs by fertilizing at appropriate intervals, it becomes pretty much a nonissue; whereas, you can expect it to be a problem if you don't fertilize at appropriate intervals.

    As a basis for comparison, setting aside issues related to water retention, I would be much more concerned about N immobilization if I were using unfinished compost as the primary fraction of a container medium rather than conifer bark because cellulose remaining in the compost is comparatively easy for soil life to break down.

    Al

  • chamaegardener (Z5) Northeast Illinois
    10 months ago
    last modified: 10 months ago

    I think the expense of Al's gritty mix is a matter of scale.

    My first trial batch was small and the Turface and pine bark were easily ordered from Etsy and shipped to me. I did find cherry stone grit on Amazon and it was $35 delivered.

    When I saw how little that made relative to the containers I wanted to fill, I started looking for better deals. As far as pine bark, I ordered a larger amount from BonsaiJack and that seemed to address the expense of that component. I went to the Turface website for the second batch and found a local (Chicago area) dealer where I can buy 50lb bags for $25. Turface has great bulk for little weight, so should stay a moderate cost. The main issue is that sifting the Turface yields only about 1/3 usable material if I want to filter out both the fines and the smaller pieces (see post above). I now found a purpose for the fines/smaller pieces in my rain garden. I then ordered a second cherry stone grit but it is obviously a cost issue because the 50lb weight causes high shipping costs, while its density provides little in the way of bulk.

    For this latest batch and going forward, I feel like I hit the jackpot by finding cherry stone grit for $8 per 50lb bag from a farm supply store. It is about an hour one-way drive though, so I am stocking up.

    I thought this might be useful for those discussing the higher cost of gritty mix materials. The more your needs, the more you save by searching out the materials in bulk. I am still on the lookout for quantity of screened pine bark though.

    tapla thanked chamaegardener (Z5) Northeast Illinois
  • Gregório Miranda
    9 months ago
    last modified: 9 months ago

    Hi guys,

    I've been in a long journey to find something as complete with the 3:1:2 ratio like Foliage Pro here in Brazil. Finally, I've found a decent alternative, but I'm not sure about the amount of Sulfur it delivers (maybe it's too much?).

    Can you help me to judge? The secondary nutrients' proportion are:

    • Ca 1%
    • Mg 0,5%
    • S 2,4%

    For comparison, Foliage Pro has:

    • Ca 2%
    • Mg 0,5%
    • S 0,05%

    That's a huge difference.

  • tapla
    Original Author
    9 months ago

    What about the NPK %s?

    Al

  • Gregório Miranda
    9 months ago

    In this one NPK %s sound quite good: N 10%, P 3%, K 5%.

    It also has all the micronutrients.


    I'm also considering another option that's not quite as optimal and doesn't have sulfur, but could be associated with gypsum.

    N 8%, P 3%, K 8%, Ca 1%, Mg 1% + micronutrients

  • tapla
    Original Author
    9 months ago

    The Ca:Mg ratio should be somewhere between 2:1 and 5:1 respectively, but you can increase the Ca level (if ever necessary) and/or S content with gypsum (CaSO4). If any of the nutrients are sourced from a sulfate compound, you won't have S issues unless you get lax when it comes to fertilizing intervals.

    On your fertilizer label, is P listed as a weight % of P2O5 (phosphorous pentoxide)?

    Al

  • Gregório Miranda
    9 months ago

    Nice, so the first fertilizer I mentioned looks quite fit. It has 2:1 Ca:Mg, an almost perfect NPK %, and contain some sulfate.


    Ah, and yes, they list P as a % of P2O5. Is it ok?

  • tapla
    Original Author
    9 months ago

    Looks like your efforts paid off. Strong work!

    Al

  • Gregório Miranda
    9 months ago

    Thanks Al, for your ever original in-depth post and your kindness :)

  • tapla
    Original Author
    9 months ago

    I've come to look at spending time here at GW/ Houzz as a natural extension of my own growing experience, and find that helping others get more from their growing experience is almost as rewarding my own growing adventures. Take good care!

    Al

  • chamaegardener (Z5) Northeast Illinois
    9 months ago

    You never understand more about what you yourself know as when you have to reduce it to be understandable to those who don't know what you know.

    tapla thanked chamaegardener (Z5) Northeast Illinois
  • tapla
    Original Author
    9 months ago

    "If you can't explain it simply, you don't understand it well enough." ~ A Einstein

  • Dom
    8 months ago

    My plants have been thriving after a year of using 511 and gritty mix. Thanks @tapla and to the other members of this forum. Here is my philo collection in gritty mix



    Since it's mostly dry and warm here in Sydney, im using pine bark fine, diatomaceous earth (DE) and pumice for my gritty mix. Watering every week even during winter and I never had issues with overwatering.


    Now I need to make another batch of gritty mix but DE hasn't been available for several months now. I'm thinking of replacing it with either perlite or scoria rock. Which one is better? Thanks

    tapla thanked Dom
  • tapla
    Original Author
    8 months ago

    Thanks for the kind words, Dom. Can you get calcined clay similar to Turface MVP or Seramis (widely available in Europe ..... don't know about Oz)?

    Al

  • Dom
    8 months ago

    Hi Al. Unfortunately I searched for weeks but didn't find a local source of Turface here. I'll be getting pine bark and pumice tomorrow so i just need another ingredient. I'm leaning towards scoria

  • Seth
    7 months ago

    Hi Al,
    Can you remind us Foliage Pro users how much Epsom Salt we should be adding to our waterings? Or if there are any other nutrients that Foliage Pro doesn’t provide?

    It’s hard to find old posts where this has been brought up.

    Thanks

    tapla thanked Seth
  • tapla
    Original Author
    7 months ago
    last modified: 7 months ago

    Foliage-Pro 9-3-6 has all essential nutrients (in a very favorable ratio for the average plant) plants normally secure by way of the root pathway, so there is no need to supplement with Epsom salts for the magnesium therein. Liebig's Law of Limiting Factors states the most deficient nutrient limits plant growth and increasing the supply of non-limiting factors will not increase plant growth. Only by increasing most deficient factor will the plant growth increase. There is also an optimum combination of the factors and increasing them, individually or in various combinations, can lead to toxicity for the plant. This means that when using FP 9-3-6 regularly, dosing with Epsom salts for the magnesium content is far more likely to be limiting than beneficial. Too much of any nutrient has the same potential to be limiting as a deficiency.

    Discussions about using Epsom salts as a source of magnesium has always pivoted on the fact that the fertilizer in use did/does not contain a source of magnesium. They're hard to find because a large number of growers who roam these pages have switched to FP 9-3-6. Before switching, I and many others were using Miracle-Gro 24-8-16 or 12-4-8, both of which, like FP 9-3-6, are 3:1:2 ratio fertilizers. Unfortunately, they lack Ca and Mg, and derive their N from urea, which tends to produce coarser growth - larger leaves and longer internodes. FP 9-3-6 derives more than 2/3 of its N from nitrate sources and none from urea, which is a major plus if you want full/compact plants.

    Al

  • RoseMe SD
    7 months ago

     hi Al! I tried getting in touch with the company that manufacturers FP 9_3_6 but they don't pick up phone or answer emails. Very frustrating. I hope you have answers to the following questions....
    Do you know how stable the solution is after dilution? After making the 1 gallon to fertilize my orchids, do you think I can keep them in a spray bottle and use it within two weeks without it going rancid?
    Also, does it contain adequate calcium so no additional supplement (e.g., eggshells) is needed?
    Finally, now the temperature is cooler at low 50  or 40s at night in CA, should fertilizer be withheld or at least, decreased in either frequency or concentration?
    Thanks.

    tapla thanked RoseMe SD
  • tapla
    Original Author
    7 months ago
    last modified: 7 months ago

    Good questions, but why are we keeping fertilizer solution in a spray bottle?

    "Do you know how stable the solution [FP 9-3-6 mixed with water) is after dilution? After making the 1 gallon to fertilize my orchids, do you think I can keep them in a spray bottle and use it within two weeks without it going rancid?" I store r/o water in gallon jugs, to which I add a small measure of FP 9-3-6 as required. I noticed last spring that I had a gallon jug about 3/4 full with the solution after I had moved all plants from the basement grow room outdoors; so, the 3/4 full container sat on the shelf under one of the grow tables from mid-may until almost November with no problem. Now, w/o the grow lights on, I would consider the basement environment to be cool and fairly dark, as the grow room is in an unfinished part of the basement and we seldom have reason to go there in the summer months. Short answer is, it's quite stable in a cool (65* or lower) spot that's not terribly bright. In a bright spot, I might expect some algae to grow, but that wouldn't diminish the effectiveness of the solution.

    "Also, does it contain adequate calcium so no additional supplement (e.g., eggshells) is needed?" Eggshells are almost entirely CaCO3 (calcium carbonate), which is considered insoluble at pH levels at which most plants are grown;so, unless it's ground into a fine powder like talc, mineralization occurs at less than a snail's pace. Ditto for bone meal. For all intents and purposes, both would best be considered insoluble with regard to container culture. The good news is, FP 9-3-6 contains soluble Ca and Mg both, at a favorable ratio. The ratio at which Ca and Mg are present in the grow medium is important because these 2 elements are well known mutual antagonists. That is to say an excess of either can and does limit uptake of the other; so, tinkering with the amount of either nutrient should be done in consideration of how it affects uptake of the other.

    In my reply above this one, I made bold the statement There is also an optimum combination of nutrients and increasing them, individually or in various combinations, can lead to toxicity for the plant. FP 9-3-6 already has a ratio of nutrients which has been optimized for use on a wide variety and a very high percentage of plants - perhaps as high as 95%; so I try to use wording that discourages growers still working toward their green thumbs from adding a little extra this or that because they heard it was good for a plant.

    I gave a lot of consideration to what our goal should be when fertilizing our containerized plants. This is what I came up with:

    Nutritional Supplementation - Objective

    Whenever we discuss what is or isn't an appropriate part of the methodology we use to make certain our containerized plants get all the nutrients essential to growth and a high state of vitality, we would probably first want to be sure our objectives are on target. It's difficult to argue with the idea that our focus in supplying supplemental nutrition to our plants should be on ensuring all nutrients plants normally assimilate from the soil via the root pathway are A) IN the soil and available for uptake at all times, B) in the soil in a favorable ratio - that is to say in a ratio that closely mimics the ratio at which the plant actually uses the nutrient, C) at a concentration high enough to ensure no nutritional deficiencies, D) yet still low enough to ensure the plant's ability to take up water, and the nutrients dissolved in that water won't be impeded (by a high concentration of solubles in the soil solution).

    At this point, you can accept these premises as worthy goals or argue against them. If accepted, we should then necessarily examine our efforts at supplementation in the light of whether or not our efforts bring us closer to or limit our ability to see the goals implemented.

    "..... now the temperature is cooler at low 50 or 40s at night in CA, should fertilizer be withheld or at least, decreased in either frequency or concentration?" Plants can safely store large quantities of (N)itrogen in nitrate form, but cannot store much N in the form of ammonium. When temperatures are below 55*F, the grow medium is saturated, or media pH is acidic, ammonium build-up in the plant can be caused by fertilizers containing urea or other forms of organic N (blood/ horn/ hoof/ feather/ alfalfa/ cottonseed meals, .....). Under more favorable conditions ammoniacal-N is converted to nitrate-N by nitrifying soil bacteria, thereby reducing the potential for ammonium toxicity. The reason we need to be on guard when media is wet, cold, or acidic is, these conditions limit the function of nitrifying bacteria or kill them altogether, which leads to the plant taking up N directly in ammoniacal form which can cause ammonium toxicity.

    Since we know that FP 9-3-6 contains no urea and more than 2/3 of its N is from nitrate sources, you can safely use it until soil temps drop into the low 40s. Ammonium toxicity is far more common than most growers might think. While the symptoms are conspicuous, they are commonly misdiagnosed as something fungal or bacterial, or over/ under-watering.

    Al

  • RoseMe SD
    7 months ago
    last modified: 7 months ago

    So helpful. You are the best Al, thanks! Oh spray bottle comes in handy for fuzzy orchid plants that need soil to "stay moist without completely dry" in a small size pot indoor. Instead of watering three times a week I mist them. I figure weak fertilizer in it can't hurt? Don't you mist your bonsai too?
    Now, do you have another thread on bush snail and how to get rid of them? Unfortunately I bought a bunch of it and eggs unknowingly with a zygopentelum pot, and the snail speed is apparently lightning speed. They are in other orchid pots now.

    tapla thanked RoseMe SD
  • Seth
    7 months ago

    Al, your replies are always very much appreciated. I could have sworn at one point you mentioned Foliage Pro was lacking in one or two key ingredients (which I thought were Mg and Ca, even though I see they are listed) although perfectly balanced for all the others. Is it possible you at one point though FP didn't have enough Ca&Mg, although you did just state they are favorable? It's very possible I'm mistaken, I certainly do remember you mentioning adding Epsom Salt to make up for fertilizer deficiencies (like in MG).


    I, like others here, have switched to Foliage Pro on your recommendation. Compared to you I am a novice although everyone I personally know thinks I'm a plant genius. The only advice I have to offer my friends are the very things I simply learned from you. I don't have time fully understand this myself, and I have many other hobbies and interests. Just following your advice has been a huge help.


    Very interesting to learn about Urea in MG vs the way FP uses Nitrate sources. I just bought a sac of Urea to experiment helping break down wood chips. I live in Colorado and can't keep compost outside because of bears. I regularly receive wood chips to aid my yard in a permaculture way, unfortunately most are pine because of where I live. Not sure if urea will be an ideal nitrogen source, but it's the most densely packed. Definitely not a permaculture product as greens or food compost items would be, but greens are very lacking and food bad because of the animals. It's just an experiment. Urea is used for Agriculture and interesting to learn about the coarser growth.


    In regards to your reply to RoseMe SD, I did not know about Egg Shells and Bone Meal insolubility in containers. I assume it's not much better in garden soil? I have Vermiculture bins with thousands of worms and I had read the worms need the Ca to make their eggs, and that egg shells were the perfect source. I wonder if it's true they can eat them.

    tapla thanked Seth
  • tapla
    Original Author
    7 months ago

    I could have sworn at one point you mentioned Foliage Pro was lacking in one or two key ingredients (which I thought were Mg and Ca, even though I see they are listed) although perfectly balanced for all the others. Is it possible you at one point though FP didn't have enough Ca&Mg, although you did just state they are favorable? It's very possible I'm mistaken, I certainly do remember you mentioning adding Epsom Salt to make up for fertilizer deficiencies (like in MG). The 'reasonable man standard' suggest we must make allowances for all manner of incongruous statements, so it's possible I might have said that once when I was really tired or just not thinking clearly or paying attention. It's happened before. I will say though, from the first day I read the analysis of what is in FP 9-3-6, even before I had used it, I knew it was going to be my 'go to' fertilizer, not in small part because it contained both Ca/Mg, nutrients I was painfully aware were missing from the 2 Miracle-Gro fertilizers (24-8-16 and 12-4-8) I was using at the time, along with 2 or 3 micronutrients. Of all the advantages offered by FP 9-3-6, perhaps the most significant is it offers complete nutrition from a single source. Since I was excited about that discovery and used it to urge others to 'follow me over' to Dyna-Gro, I wouldn't ever have forgotten that fact, but that doesn't mean that somewhere along the line I didn't mess up and make a mistake. I catch mistakes all the time when I take time to proof read, so I know some mistakes make it to the forum when I'm pressed for time and don't proof carefully.

    I think the discussions you refer to involved the idea that lime could raise the pH of the gritty mix too a level too high for some plants, so the fix was to skip use of lime and use gypsum and Epsom salts as a source of Ca/Mg respectively, this because these compounds have no (or very little) effect on pH levels. That practice continues to be valid when using the gritty mix, but it's soo much easier to just switch to FP 9-3-6 and do away with 2 steps rendered superfluous bu the change.

    I, like others here, have switched to Foliage Pro on your recommendation. Compared to you I am a novice although everyone I personally know thinks I'm a plant genius. The only advice I have to offer my friends are the very things I simply learned from you. I don't have time fully understand this myself, and I have many other hobbies and interests. Just following your advice has been a huge help. I appreciate you taking that 'leap of faith'. I realize the best way to get people to pay attention to what I say is by doing all I can to maintain my credibility. I do that by operating well within the limits of my knowledge. You might have noticed I can always support what I say with sound reasoning and science, and almost all of the things I discuss have been tempered with a large measure of practical application.

    I can't help but think back to before the internet before all earthly knowledge and then some was immediately available at our fingertips. If I started with an outline, most of the important things I learned in the first 4 years studying texts could be typed out in a week or two on a keyboard. When I think about how valuable that information has been to my own growing experience, it's difficult to think it wouldn't be equally valuable to others working toward a green thumb. With that in mind, I made helping amenable others to get more from their growing experience become an extension of my own growing experience.

    Eggshells.

    Even if you were to 'process' eggshells in a blender or food processor with water, the resultant pieces would still be too large to 'feed' the worms. In fact, thee razor sharp edges can rip the outer skin as worms crawl over the shells, and small ingested pieces that are too large can damage the intestinal tract and cause death. Eggshells are safe for worms when they are crushed into a very fine powder, like talc. They are also more likely to release Ca into soil or grow media when supplied in an extremely fine powdered form. Archeologists are forever digging up shell fragments of ducks, chickens, and other fowl that are still identifiable, by eye, insofar as what type of fowl laid them, so we shouldn't resort to adding crushed eggshells to increase availability of Ca to our soils or container grow media.

    It's unusual for mineral soils to be deficient in Ca, and if eggshells did work to increase available Ca, we'd see more issues related to a deficiency of Mg caused by an excess of Ca (antagonistic deficiency).

    Al

  • four (9B near 9A)
    7 months ago
    last modified: 7 months ago

    I understand that the reason for failure of terrestrial plants (excluding marsh types) in contInuously wet soil is deficiency of air in the soil.

    In a tub of stationary unsupplemented water I have kept individual Elders and Porterweeds permanently for years, growing /thriving; also other kinds for very long periods.

    The amount of air in the water is sufficient?

    tapla thanked four (9B near 9A)
  • tapla
    Original Author
    7 months ago

    Physiologically, you will find roots of aquatic or inundated living plants to be much different than roots of terrestrial plants, this, due to development of aerenchymous tissue (a tissue with a greater percentage of intercellular air spaces, which allows oxygen used to burn food/sugar and drive root metabolic processes to enter the plant above the inundated portion of the plant and diffuse through root tissues) as opposed to the normal normal parenchyma tissue of terrestrial plants.

    Aerenchyma is filled with airy compartments and channels. It usually forms in already rooted plants as a result of highly selective cell death and dissolution in the root cortex in response to hypoxic conditions in the rhizosphere (root zone). There are 2 types of aerenchymous tissue. One type is formed by cell differentiation and subsequent collapse, and the other type is formed by cell separation without collapse ( as in water-rooted plants). In both cases, the long continuous air spaces allow diffusion of oxygen (and probably ethylene) from shoots to roots that would normally be unavailable to plants with roots growing in hypoxic media. In fresh cuttings placed in water, aerenchymous tissue forms due to the same hypoxic conditions w/o cell death & dissolution.

    Note too, that under hypoxic (airless - low O2 levels) conditions, ethylene is necessary for aerenchyma to form. This parallels the fact that low oxygen concentrations, as found in water rooting, generally stimulate production of ethylene.

    Al

  • four (9B near 9A)
    7 months ago
    last modified: 7 months ago

    Beautifully composed, I'll call it Alegant.

    From it, I understand that both [a cutting] and [a parenchymouslly-rooted plant previously in solid medium] grow in water because aerenchymous roots form to conduct oxygen and ethylene for diffusion into the water. Do you happen to know why aerenchymous roots do not form likewise in saturated soil to diffuse oxygen and ethylene into that water?

    tapla thanked four (9B near 9A)
  • chamaegardener (Z5) Northeast Illinois
    7 months ago

    Is there merit to airpots? (Example) They seem to be based on providing more air within the root zone, similar in theory to Als Gritty Mix. Thinking it through though, if regular garden soil is used then the only air introduced is when the roots reach the outside of the pot. But if the gritty mix is used, then perhaps more air would be introduced throughout the root zone?


    I foresee an issue though with overwintering, where sinking them in the garden might introduce smaller undersireable particles into the gritty mix.

  • tapla
    Original Author
    7 months ago

    From it, I understand that both [a cutting] and [a parenchymouslly-rooted plant previously in solid medium] grow in water because aerenchymous roots form to conduct oxygen and ethylene for diffusion into the water. Yes. A terrestrial plant unable to transition between its root's cortex being filled with parenchymous tissue to a cortex filled with aerenchymous tissue is highly unlikely to remain viable under stress of long term inundation.

    Do you happen to know why aerenchymous roots do not form likewise in saturated soil to diffuse oxygen and ethylene into that water? They can and often do. the problem is, the roots of inundated plants do not need to be very efficient at water uptake because they are, after all, inundated. A root with its cortex filled with aerenchymous tissue, once the soil dries down and air returns, are so limited in their ability to extract water from container media that isn't unsaturated that severe dieback or collapse of the entire organism is often the result. IOW, many plants finding themselves inundated can adapt to a saturated rhizosphere by revamping root structure, but they cannot easily transition back and forth between being grown in an inundated medium and one which is suitable aerated for use in conventional container culture. You can ask almost all plant candidates to grow under conventional container culture and a large fraction to grow under conditions of inundation; but, the fly in the ointment comes from asking the plant to make the transition cyclically.

    Thanks for the kind words.

    Al

  • tapla
    Original Author
    7 months ago

    Is there merit to airpots? Yes. They are designed such that when roots reach the perimeter of the soil mass they are killed by desiccation; then, just as in a branch with the growing tip (the apical meristem)removed, the root back-buds and the new branches hopefully grow outward from the center of the root mass. The added gas exchange due to the perforations in the pot sidewall(s) also helps the soil to dry down faster, which is helpful to root health. Within reason, the media or growing set-up that actually requires watering more often is going to allow the grower to provide plants with a better opportunity to realize more of their genetic potential. They seem to be based on providing more air within the root zone, similar in theory to Als Gritty Mix. They work to some degree in that fashion, but a well-aerated grow medium is the best way to increase gas exchange and ensure the medium doesn't remain saturated long enough to be a serious and cyclic limitation that robs plants of a large fraction of their potential in terms of growth rate, vitality, appearance, and yields where applicable. Thinking it through though, if regular garden soil is used then the only air introduced is when the roots reach the outside of the pot. Yes, the finer the materials used to make the medium, the less effective the air pots will be. But if the gritty mix is used, then perhaps more air would be introduced throughout the root zone? True by virtue of the fact the gritty mix doesn't just have a random macropore here and there between soil particles. The pores are so abundant they link together to form a labyrinth of channels throughout the entire soil column through which air can move ...... and a gas disperses in air more than 10,000 times faster than in water.

    I foresee an issue though with overwintering, where sinking them in the garden might introduce smaller undersireable particles into the gritty mix. If the planting is established and the entire soil column is filled with roots, as one might expect the case to be as fall/winter arrives, it wouldn't be much of an issue at all. I'd just take my trusty hemp whisk broom and brush the fine particles away. It works amazingly well for brushing small soil particles and other detritus from the top of the soil.


    Al


  • chamaegardener (Z5) Northeast Illinois
    7 months ago
    last modified: 7 months ago

    Thank you Al!

    Do you use airpots?

    Do you think Al's Gritty Mix in an airpot would deliver (better similar or worse) results for growing bigger arborvitae, connifers and maples from #1 and #3 plants than the same gritty mix in a regular planter with bottom hole(s)? My general goal is to get the biggest above-ground plants for the available planter root space while keeping them alive against overwatering using your mix. At some point I may cut back the roots and limit going into ever bigger planters which is sort of but not really bonsai, or I may plant them in the yard as they mature.

    Chamae

    p.s. This will be my first spring replanting (i did plant one in summer that led me to the mix but was already gone). Some are in the planters I purchased then sunk into the garden, some are ordered to come. Sufficient Al's gritty mix is ready.

  • Seth
    7 months ago

    I think the discussions you refer to involved the idea that lime could raise the pH of the gritty mix too a level too high for some plants, so the fix was to skip use of lime and use gypsum and Epsom salts as a source of Ca/Mg respectively, this because these compounds have no (or very little) effect on pH levels. That practice continues to be valid when using the gritty mix, but it's soo much easier to just switch to FP 9-3-6 and do away with 2 steps rendered superfluous bu the change.


    YES! I believe this is where I'm mistaken. Maybe I had tunnel vision about the Lime issue which was mentioned in your earlier recipes. Or maybe I thought Foliage Pro was soluble so didn't contain it properly? Regardless, I'm sure the error was on my part. It's just funny for the past 10 years I've been worrying about when to find the time to eventually address this. I'm happy to know using Foliage Pro I need nothing else.

  • skysong4
    5 months ago

    There has been a great deal of discussion on preventing overwatering, but I'm curious about the frequency at which you need to water plants in these much more aerated soils, to prevent issues from underwatering, and how you handle that.


    I'm growing mostly indoors in the Northeast US, and in my experience, I've had far more plants die from underwatering than overwatering. I've also actually had plants in fairly porous soil mixes fail to thrive (for example, hoyas in chunky bark mixes, some plants I tried in 5-1-1, and even orchids), but then show fantastic growth when either watered extremely frequently with extra water sitting in a deep saucer to be absorbed later, or switched to a less porous media (peat-based mix similar to ProMix). I suspect part of this is that with "normal" watering like I'd use for a houseplant in a peat-based mix, the water-retaining portion of the coarse mix simply didn't have enough time to fully absorb the water quickly running over it.


    I've had amazing success with African violets and other moisture-loving plants in a wick-watering setup, where the plants are in a fairly airy, porous mix (50% perlite, 40% peat or cocoa coir, and 10% vermiculite) with a wick (acrylic yarn in my case) that hangs down into a water reservoir below the potted plant. I'm guessing this works so well because the mix is relatively aerated while also continually moist. This is at the scale of a mini plant in a condiment cup set in the mouth of a Mason jar, though, and the plants themselves have pretty fine roots in scale with the relatively fine mix. I'm wondering how to best modify this method to use at a larger/coarser scale for the rest of my houseplants, which I've noticed tend to suffer from my infrequent watering schedule. In a way, I'm thinking that this is similar to passive hydroponics, sometimes called "semi-hydro", where the lower portion of porous media itself (like expanded clay leca pellets) sits in a pool of water and wicks water upwards to the media not in direct contact with the water pool.


    I'm trying to figure out what media to use for such a purpose. Do you think either of the methods I described would work in combination with your 5-1-1 mix, or your gritty mix? Would there be enough wicking capability in the media to pull sufficient water from a wick or saturated media below? Any thoughts on using a calcined clay product alone, if being submerged like in passive hydro would not be great for the pine bark?

  • beccaboo_
    5 months ago

    @tapla Al, thanks so much for your dedication to this topic. I’m mostly an outdoor plant girl because I have pets but this is the first year I set up a greenhouse for some container plants during the winter. I had a terrible problem with fungus gnats and turned to your mix. They got better but are now back again. How much is too much dust mixed in with the 5:1:1 mix? I’m sure I over watered again being worried about the heater constantly running in my greenhouse. I’ve separated the sizes of pine bark to 4 containers. 3/8, 1/4, 1/8 and dust. Is there a good ratio to keep the water flowing? I admit, I am a waterholic. I’ve used the tell method but catch myself not using it sometimes.


    Also, what is a good screen size for pearlite, I used miracle gro and didn’t screen it till after I started implementing better habits. i just used a window screen size mesh but there was a ton of small pieces. I found some course pearlite but it still has some dust. What size of the pearlite is too big? Again, thank you for sharing your knowledge. I’ve really enjoyed learning from you.

    tapla thanked beccaboo_
  • tapla
    Original Author
    5 months ago

    I'm pleased to make your acquaintance, Becca, and thank you for the kind words. All who give advice here like to think it is helping others get more from their growing experience, so it's easy to image how much we enjoy having our efforts validated.

    If you have a working knowledge of the concept that drives how the media I use are put together, you might know that if all the particles that make up a medium are larger than 1/10", the medium will for all intents and purposes be incapable of holding anything more than a negligible amount of perched water. The dust or very fine material you inquire about is allowed to remain included in the mix not because it's beneficial or essential to the plant, but because it is more convenient for the grower to water every 406 days instead of every other or every third day.

    The gritty mix should be carefully screened to eliminate dust and the finest of particles, and it's would be essential to do the screening if the intent is to do away with as much perched water as possible. If someone is tempted to start adding peat or coir or compost to the gritty mix "to increase water retention" because they "heard" it doesn't hold enough water, they will have eliminated the reason they made it in the first place. I don't mean to get off into the weeds by mentioning the gritty mix when you asked about the 5:1:1 mix, but the point being made is valid for either. When we're implementing the concept behind the media, we're presumably looking to offer our plants the best opportunity we can, to realize as much of their genetic potential as possible. Ideally, the level of dust and fines would be very low - only a % significant enough to provide the grower with watering intervals they can work with. The plants will still be perfectly happy if we situate them in a medium that requires watering several times per day, but we as growers need to compromise when the order of our priorities dictates that having a job is more important than watering plants every day or every other day. Personally, I prefer growing in media that requires me to water a planting about every 3rd day, even though plants might do better in a medium that holds less water.

    So, when it comes to media's ability to hold water, less is almost always going to be better (but there will be a point at which too little water will lead to diminishing returns) from the plant's perspective, even if it requires extra time watering and fertilizing more frequently. If that's something the grower can't or won't deal with, it's up to the growers to determine what's right for themselves. Very often we find what is truly best for the plant and what is best for the grower ere mutually exclusive.

    Why not make a small amount of 5:1:1 mix with pine bark in the 1/8-3/3 size range, and no peat or bark fines, and try a few plants in that? I guess it would then be a 5:1 mix. Mark the pots as special and see what you find about A) how often they need water, and whether or not you're willing to make the extra effort, and B) how the plants take to it. When you compare the 'experimental plants' to what you know from growing other plants in the 5:1:1 mix, you should have a very good idea about what direction you want to take.

    Pine bark, with it's flat particles is somewhat unique in that perlite which is quite fine can get wedged between 2 particles of bark and create a very large pore space, so the size of the perlite is less important when using pine bark than it is when someone is trying to amend peat, coir, compost, ...... with perlite.



    Generally speaking, medium is fine for 5:1:1, but coarse will work fine, too. For media with large fractions of peat or other fine particulates, coarse, and lots of it, are the better choice.

    Al

  • RoseMe SD
    5 months ago

    Doesn't pearlite also help with water retention while creating circulation? So by definition, it is like a space holder for air while storing extra moisture? The only thing I worry about using pearlite is that it may scratch the fine roots when I pack the media in.

  • tapla
    Original Author
    5 months ago
    last modified: 5 months ago

    In science, a fluid is a liquid, gas, or other material that continuously deforms (flows) under an applied shear stress, or external force. Grow media are technically fluid and as such they can be displaced. Displacement is described as the occupation by a submerged/immersed body or part of a body of a volume which would otherwise be occupied by a fluid. When we drop a marble into a glass filled to the brim with water, the marble displaces its own volume in water, so a measure of water equal to that displaced overflows the brim of the glass. When a particle of perlite is added to a container filled with water-retentive medium, the same thing occurs, so the perlite particle reduces water retention by virtue of the fact it displaces it's own volume of medium and the moisture it is capable of holding.

    To continue the discussion, I think it's important to understand A) where the perlite particle is located in the soil column changes the degree of it's usefulness, and B) what is meant by the term 'container capacity' (CP), which can be described as the measure of how much water grow medium in a container holds at the moment it has stopped draining after having been watered to the point of complete saturation.

    Imagine a 10" pot filled with a medium that supports 4" of perched water at CP. The perlite particles situated in the fraction of the soil column capable of holding perched water (the bottom 4") are very useful in that they occupy space which would otherwise be filled with with medium we know will be 100% saturated with water at CP. Unfortunately, the perlite does little or nothing to increase the level of aeration within the fraction of the soil column that holds perched water; this, because water within the perched water table fills ALL air space, even those that provide small air pockets on the surface of the perlite particles. Since the top 6" of medium is incapable of holding perched water and should generally provide an adequate oxygen supply for most plants, perlite in that fraction of the soil column becomes pretty much superfluous.

    Perlite does contain internal pockets of air, but these are not open pores which would add to porosity. Think of someone adding dozens of ping pong balls to a medium to increase air porosity because, after all, 'they are filled with lots of air'. Perlite is much the same. While its highly irregular surface is capable of adding some air porosity to the fraction of a soil column where no perched water is held, we must realize that the amount of air porosity it can add to media comprised of fine particles can be nowhere near the volume of air and medium displaced by the particle. So, adding a perlite particle to any given volume medium REDUCES o/a aeration and continues to do so until there is a volume of perlite so large that there is no longer enough fine material to fill all the air spaces between the perlite particles.

    This brings us back full-circle to the idea that, 'if we want to build a medium which provides the benefits of higher aeration and better/more complete drainage, it's essential to start with a very large fraction of coarse material (80% or more), because trying to amend a medium deemed too water-retentive will take us the opposite direction we intended to go before it gets better'.







    Notice how the images (page 3) show how adding large particles thinking we're amending media based on materials too fine actually decreases aeration until we get to the "threshold proportion", which occurs at the point there is no longer enough fine material to fill all the spaces between the coarse particles.

    Al

  • skysong4
    5 months ago

    @tapla Hi Al, I posted just above Becca, with some questions on watering frequency for plants in 5-1-1, and am looking for thoughts on whether 5-1-1 might work well as the media in a water wicking setup, to allow for less frequent watering. Would you mind taking a look? Thanks!

  • chamaegardener (Z5) Northeast Illinois
    3 months ago

    60mph gusting winds today. My largest container plant in gritty mix, a 3ft tall 4ever goldy arborvitae, blew over with roots pulled out of mix. I planted it back so hopefully it works out.


    I tried watering the mix to give it more weight and cohesion as the gusts grew fiercer but ultimately I had to move the planter to a less windy location after getting the roots tucked back in.

  • tapla
    Original Author
    3 months ago




    trucker's hitch (knots) ^^^

    String tied to wire loops, ^^^ which go through holes in the bottom of the pot.

    Al


  • chamaegardener (Z5) Northeast Illinois
    3 months ago

    I see. Another unknown unknown to be fixed next spring.

    tapla thanked chamaegardener (Z5) Northeast Illinois
  • RoseMe SD
    3 months ago

    Back to the pearlite and aeration, it seems larger size pearlite will be superior than those tiny particle pearlite sold at HD. Do tiny pearlites serve any useful purpose in ether potting soil or barks?

  • four (9B near 9A)
    3 months ago

    Media, roots : a comparison.


    The plants are contemporaries.

    tapla thanked four (9B near 9A)
  • Josh
    2 months ago

    Hi Al, everyone,


    I've a kinda ignorant question: what would happen if I tried to grow plants in 100% bark, leaving the perlite and peat out. Would the bark simply collapse without the perlite adding some shape heterogeneity? Perlite's a bit expensive here in France, and the gritty mix doesn't seem to be a good option for me as I may have to travel now and then. Most of the bark here is 10-20mm, but I did manage to find a "petit calibre", though I don't yet know if their in the 3-9mm range, but it does seem that it's implied.


    A couple of years ago, I stubbornly tried to grow plants in straight LECA (1/6 - 1/2 inch) bought off the French version of Craigslist, but it was a failed experiment. Maybe not, I learnt that it doesn't work and maybe I should try and be less stubborn :D ... I don't know if the LECA was retaining too much moisture on it's own surface (the particles seemed too large for capillary action), if I was watering/fertilizing too much, or if there was a chemical treatment on the particles, but most of my plants developed symptoms of overwatering/fertilizer burn and died off.


    This time I'm going to be sane, and just use the 5-1-1 mix, but was just curious if I could get away with using just straight bark, or what substitutes I could use for perlite and peat...


    Thanks as always!

    Josh

  • Seth
    2 months ago

    Hi Al,

    Last year you responded to someone's question about repotting their Fiddle Leaf Fig with some great information, here's the link - https://www.houzz.com/discussions/6025060/need-help-with-repot-of-fiddle-leaf-fig#n=9

    So you don't need to repeat anything you stated there, can you confirm that in fact gritty mix is perfectly fine used in any situation you would otherwise recommend the 5:1:1?

    I've had a Ficus (Weeping Fig) for years that hasn't taken off even receiving plenty of indirect light, flushing of salts, and weekly watering. It's been in gritty mix with a fabric air pot. I was considering transferring to a larger ceramic pot with it's roots in the gritty mix but using 5:1:1 around it to see if that helps.

    Speaking of which. I'll be planting a few dozen bare root shrubs (Serviceberry) outdoors in the next few weeks. Can you see an advantage of using a gritty mix if I keep the hole small considering they're bare root trees?

    You should have a donation site for "buy me a coffee" for all the help you give! thanks!

  • tapla
    Original Author
    2 months ago

    Rose - Perlite is not internally porous in that there is no way air or water vapor can enter perlite's closed cells, which hold the same gasses they held when the perlite was first vitrified. That's why aeration decreases on a per/volume basis when perlite is added to fine material. It's impossible for perlite to provide as much aeration as it displaces because perlite's rough surface is the only part that can create aeration, and it can only be a small fraction of the air in the material it displaces.

    Perlite is more effective in bark-based media than in media based on fine materials like peat, coir, compost, sand, composted forest products, ..... . The reason is, a particle of perlite in fine material like I listed will be surrounded by that fine material, providing less aeration than in the medium it displaces; in bark, perlite gets wedged between flat pieces of bark, creating very large air pocket. Lay a playing card on a table so it covers a piece of perlite and notice how much space is created between the table and the card. It is many, many times more than the volume of perlite, perhaps as much as 100x. It's still essential though, if you want to take advantage of all that aeration, you don't shoot yourself in the foot by adding too much fine material. If there are enough fines to fill the large spaces created by the perlite, there is no sense in looking for bark.

    Four - Thanks for thinking of us and providing the images!

    Josh - heterogeneity isn't necessarily a plus. In fact, it's possible to have less air space in a mixture of particle sizes/shapes than it is in a medium that has a smaller particle size than the average (particle size) of the mixture, if the smaller particles are uniform in size and shape.

    You might have some success growing in pine bark only, but don't forget to add the dolomite - CaMg(CO3)2 to bring the pH up to something that better favors the average plant. Once you get a plant to establish in a medium, the roots actually become part of the soil structure. I've seen ficus trees that have been kept in the same container so long that almost all the soil has gassed off and I could look into the pot and see the bottom in places. That's aeration!

    As I mentioned to Rose, anything gritty (and not phytotoxic) will work as well as perlite in the 5:1:1 mix. Seramis would work, as would granite chips or formaldehyde foam beads of an appropriate size. I don't know what the parboiled rice hull situation is in France, but that could be pressed into service as a replacement for peat and or perlite when used with pine bark.

    Seth asks: ..... can you confirm that in fact gritty mix is perfectly fine used in any situation you would otherwise recommend the 5:1:1? I think the gritty mix might be overkill for 1) plantings of annuals, 2) veggies other than perennial plantings, 3) naturally vigorous plants with root systems that grow so quickly they require repotting annually to keep them in top shape (hibiscus, datura, brugmansia, others. IOW, if they aren't going to be in the same soil for more than a year, and they aren't something special (sentimental value, expensive, hate wet feet), (my thought is) they can be grown in the 5:1:1 mix with little or no conspicuous difference in growth rate or vitality levels.

    I grow all my woody material and all succulents in the gritty mix, which is pretty much all I grow any more. The gritty mix might also excel at keeping plants in shallow pots healthy.

    If these pots are 12, 8, and 4" deep, and the soil in the pot supports 3" of perched water, the tall pot has 75% of the soil free of perched water at container capacity (see below), while the pot on the right has only 25%, and that's a problem.

    I was considering transferring to a larger ceramic pot with it's roots in the gritty mix but using 5:1:1 around it to see if that helps. When you mix soil textures in the same container, it's difficult to keep the soil appropriately moist. Part of the soil column can be too dry while the rest might be too wet.

    I counted the number of Ficus I have in pots and came up with 45, not counting the propagules I start out of compulsion. They are all in the gritty mix and all doing very well. I think we could figure out what's wrong if you want to try. I know for sure it's hard to beat a properly made gritty mix for woody plants.

    Can you see an advantage of using a gritty mix if I keep the hole small considering they're bare root trees? None - I would try to talk you out of it unless your soil is sand or sandy loam, then it won't matter as much. Anything else will collect water in the large spaces between the gritty mix particles. It's best to use native soil to backfill the planting hole. If the bare-root plants are really small, you might grow them out in a flat or individual containers for a year so you can plant out in early spring while they are still dormant - or, you could plant out this fall. Just try to avoid planting out in full sun, even if the plants are still dormant, especially if it is already hot where you live. We've been in the upper 70s and 80s all week. Don't know about where you live, but it's a consideration.

    BTW - thanks for the kind words.

    Al

  • chamaegardener (Z5) Northeast Illinois
    last month
    last modified: last month

    Al, I have a few technical questions about the 5-1-1 mix.


    First, why is it ok to use pine bark dust in the 5-1-1 mix when the 1-1-1 gritty mix uses screened pine bark to ensure separation of the components to allow air in the root zone? I see up thread you said the dust was alowable so watering could take place every 4-6 days instead of everyday. I get that, but why doesn't the 5-1-1 mix with pine dust create the same perched water table that is addressed by the screened components in 1-1-1?


    Also, comparing the 5-1-1 components to 1-1-1, does the perlite perform the same function as chicken grit? Is perlite used as a less expensive compromise to chicken grit? And what do the small peat particles provide? More water retention? Less water retention due to difficulty rewetting peat? Since the pine dust and smaller fines retain water already, what does peat add to that?


    Finally, would a 5-1-1 mix using screened pine bark, Turface and chicken grit perform the same as using pine fines, perlite and peat for 5-1-1? Better due to air space in the root zone? Better or worse than 1-1-1 (aside from the greater amount of organic material breaking down)?

    tapla thanked chamaegardener (Z5) Northeast Illinois
  • tapla
    Original Author
    last month

    ..... why is it ok to use pine bark dust in the 5-1-1 mix when the 1-1-1 gritty mix uses screened pine bark to ensure separation of the components to allow air in the root zone? I see up thread you said the dust was alowable so watering could take place every 4-6 days instead of everyday. About 20 years ago when I joined GW, I was in search of information re grow media I could use for bonsai in shallow pots. There was no one here using a mix that was made of predominantly, much less all, particles larger than about 1/10". Everyone (at least seemingly) was using media based on peat and either living with excess water retention or employing work-arounds that promoted a build-up of dissolved solids (salts) in media.

    Fast forward a couple of years to a point in time when I had pieced together information that yielded a understanding of PWTs and how particle size primarily drives water retention. Since I then had the same desire to share information I think is helpful that I still have today, I was anxious to share what turned my growing experience around almost completely. Selling (figuratively) the gritty mix was no easy thing. Conventional thinking was such that, if a soil wasn't rich and black it would never provide a suitable home for roots. Compost, when available, was most favored by many as the primary ingredient in their grow media; and, relating successes using the gritty mix largely fell on deaf ears.

    Then, same as now, I realized the gritty mix was more expensive and more of a chore to make, so I wanted an alternative to the gritty mix, something less expensive I could mix up inside of a few minutes and use for all my veggies and mixed display containers scattered through the gardens and decks. Putting the same concept to work, I came up with the 5:1:1 mix, which does support a PWT, but the ht of the PWT is nowhere near the height of the PWT in commercially prepared media, which commonly ranges from 4-6+ ".

    The 5:1:1 mix eventually came to be viewed as a legitimate grow medium and its use continued to grow. I think it would be much more popular if the bark which servers as its base ingredient hadn't become more difficult to find. Milled yellow pine bark, a by-product of the treated lumber industry, is now commonly sold in bulk to industrial operations who super heat it and burn the gasses produced to drive steam processes for the manufacturing sector.

    When I first started talking about the gritty and 5:1:1 mix, people were used to watering intervals measured in weeks, and few were interested in using a mix that required watering every 3-6 days. There is still a tendency to hold to the idea that these overly long watering intervals are the norm which other media should be judged against. I try to be clear in laying out the idea that there is a tax to be paid on these long intervals, and it comes in the form of lost potential in terms of growth rate, vitality levels, eye appeal, and yields when that is a factor.

    ..... why doesn't the 5-1-1 mix with pine dust create the same perched water table that is addressed by the screened [gritty mix]? It does; however, most of us are willing to make some degree of compromise when it comes to comparative degrees of 'good'. The 5:1:1 mix is meant to be far better than most commercially prepared media, it's far less expensive on a per volume basis; and, while it might not have the same potential the gritty mix has, it provides a viable choice that offers more potential than most commercially prepared mixes while freeing those unwilling or unable to make the gritty mix from the additional expense and effort.

    Also, comparing the 5-1-1 components to 1-1-1, does the perlite perform the same function as chicken grit? Not really. In the gritty mix, the grit is included almost exclusively as a way to adjust the medium's ability to hold water. As you've read, the 'formula' I usually suggest is to keep the bark fraction of the gritty mix at no more tham 1/3 of the o/a volume, and vary the ratio of Turface and grit to adjust water retention.

    Less Water:

    4 grit

    3 bark

    2 Turface

    More water:

    4 Turface

    3 bark

    2 grit

    In the 5:1:1 mix, the perlite particles work somewhat uniquely. They get wedged between flat plates of pine bark, where even a small particle of perlite can create a very large pore space. Wedge a marble between 2 sheets of plywood and use your mind's eye to envision the size of the air space. You can 'see' that a little perlite can really open up a milled bark-based medium. Is perlite used as a less expensive compromise to chicken grit? They both have their functions and in some cases could be used interchangeably if the perlite is screened. And what do the small peat particles provide? More water retention? Less water retention due to difficulty rewetting peat? Since the pine dust and smaller fines retain water already, what does peat add to that? Because the perlite really opens the medium up, there is generally not enough fine material in a bag of bark to provide the kind of water retention people are willing to deal with. The peat should be used as a way to adjust water retention. Remember, the recipes are no ore than a starting point. Ideally, readers will understand the concept well enough that, with a little time, what's required becomes self evident ....... like our grandmothers made bread.

    Al

  • chamaegardener (Z5) Northeast Illinois
    last month

    Thank you Al. Having no experience, I decided to pretty much adopt your formulas without question. Then, as I have started using them, I get these questions. I appreciate you expanding our knowledge base.

    tapla thanked chamaegardener (Z5) Northeast Illinois
  • four (9B near 9A)
    last month

    Al, in your reply, the first section ("About 20 years ago.... when that is a factor.") provides a perspective that pulled together some loose ends in my mind.

    tapla thanked four (9B near 9A)
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