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

tapla
last month
last modified: last month

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 (20)

  • tapla
    Original Author
    last month
    last modified: last month

    ~ page 2 ~

    A given volume of large soil particles has less overall surface area when compared to the same volume of small particles and therefore less overall adhesive attraction to water. So, in media with large particles, GFP (remember the weight of the water column pushing down on water lower in the pot is the Gravitational Flow Potential) more readily overcomes capillary attraction. They simply drain better and hold more air. We all know this, but the reason, often unclear, is that the height of the PWT is lower in coarse media than media comprised of primarily fine particles. The key to good drainage is size and uniformity of particles. Mixing large particles with small is often very ineffective because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential. An illustrative/ rhetorical question: How much perlite should we add to pudding to make it drain well?

    I already stated I hold as true, the grower's medium choice when establishing a planting for the long term is the most important decision he/she will make. There is no question roots are the heart of the plant, and plant vitality is inextricably linked in a hard lock-up with root vitality. In order to get the best from our plants, we absolutely must maintain roots in a healthy state.

    If we start with a water-retentive medium, we cannot effectively amend it to improve aeration or drainage characteristics by adding larger particulates. Sand, perlite, Turface, calcined DE ...... none of them will work effectively. To visualize why sand and perlite can't change drainage/aeration, think of how well a pot full of BBs or would drain; then think of how poorly a pot full of pudding would drain. Even mixing the pudding with perlite and BBs at a 1:1:1 ratio in a third pot yields a mix that retains the drainage/aeration characteristics and PWT height of the pudding. It's only after the BBs/ perlite becomes by far the largest fraction of the mix (80-95%) that aeration begins to improve. At that point, we are growing in BBs/ perlite amended with a little pudding .

    We cannot add coarse material to fine material and improve drainage or the ht of the PWT. Use the same example as above and replace the example of pudding with play sand, peat moss, or a peat-based potting medium - same results. The benefit in adding perlite to heavy (water-retentive) soils doesn't come from the fact they drain better. The fine peat or pudding particles simply 'fill in' around the perlite, so drainage and the height of the PWT remains roughly the same. All perlite does in heavy soils is occupy space that would otherwise be full of water. Perlite simply reduces the amount of water a medium is capable of holding because perlite is not internally porous. IOW - all it does is take up space. That can be a considerable benefit, but it makes more sense to approach the problem from an angle that also allows us to increase the aeration AND durability of the medium. Adding ping pong balls which are full of air adds how much aeration to a bucket of soil? It would actually reduce aeration. That is where Pine bark comes in, and I will get to that soon.

    If we wish to profit from a medium offering superior drainage and aeration, we need to start with an ingredient or ingredients as the basis for your medium that already HAVE those properties by ensuring that the medium is primarily comprised of particles much larger than those in peat/ compost/ coir/ sand/ topsoil ….., which is why the recipes I suggest as starting points all direct readers to START with the foremost fraction of the medium being coarse particles. From there, if you choose, you can add an appropriate volume of finer particles to increase/ adjust water retention. We do not have that option with a medium already extremely water-retentive right out of the bag.

    I fully understand that many might be happy with the results they get from using a commercially prepared soil, and I'm not trying to twist any arms to convince anyone to change anything. My intent is to make sure that those who are having trouble with issues related to their choice of soil, understand why the issues occur, there are options, and what they are.

    We have seen that adding a coarse drainage layer at the container bottom does not improve drainage. It does though, reduce the volume of required to fill a container, making the container lighter. When we employ a drainage layer in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This simply reduces the volume of soil available for roots colonization. Containers with uniform particle size from top of container to bottom will yield better/ more uniform drainage and have a lower PWT than containers using the same medium with added drainage layers. The coarser the drainage layer, the more detrimental to drainage it is because water is more (for lack of a better scientific word) 'reluctant' to move downward because the capillary pull of the medium above the drainage layer is stronger than the GFP. As mentioned, the reason for this is, there is far more surface area on particles for water to be attracted to in the medium located above the drainage layer than there is in the drainage layer, so the water 'perches'. I know this goes against what most have thought to be true, but the principle is scientifically sound, and experiments have shown it as so. Many nurserymen employ what are termed the 'pot-in-pot' or the 'pot-in-trench' method of growing to capitalize on simple science to be rid of the limitations associated with PW.

    If you discover you need to increase drainage, you can simply insert an absorbent wick into a drainage hole & allow it to extend from the saturated medium in the container to a few inches below the bottom of the pot, or allow the wick to contact soil below the container so the earth acts as a giant wick, pulling all or most of the perched water from the medium in the container (see images in the OP). Eliminating the PWT has much the same effect as providing your plants much more medium to grow in, as well as allowing more, much needed air into the root zone.

    In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they suffer/ die because there is a volume of air in the root zone insufficient to insure normal root function, so water/nutrient uptake and root metabolism become seriously impaired.

    To confirm the existence of the PWT and how effective a wick is at removing it, try this experiment: Fill a soft drink cup nearly full of a water-retentive medium. Add enough water to fill to the top, being sure all the medium is saturated. Punch or melt a drain hole in the bottom of the cup and allow the water to drain. When drainage has stopped, insert a wick, or even a toothpick into the drain hole. Take note of how much additional water drains from the cup. Even touching the medium with a toothpick through the drain hole will cause substantial additional water to drain. The water that drains is water that occupied the PWT. A greatly simplified explanation of what occurs is: The wick or toothpick 'fools' the water into 'thinking' the pot is deeper than it is, so water begins to move downward seeking the 'new' bottom of the pot, pulling the rest of the water in the PWT along with it (because water sticks to itself). If there is interest, there are other simple and interesting experiments you can perform to confirm the existence of a PWT in containers, and I can expand later in the thread.

    I always remain cognizant of these physical principles whenever I build a medium. I have not used a commercially prepared medium in many years, preferring to build or amend one of my 2 basic mixes to suit individual plantings. I keep many ingredients at the ready for building soils, but the basic building process usually starts with conifer bark and perlite. Sphagnum peat moss plays a secondary role in my container media because it breaks down and compacts too quickly to suit me, and when it does, it impedes drainage and reduces aeration.

    Size matters. Partially composted conifer bark (pine is easiest to find and least expensive) works best in the following recipes, followed by uncomposted bark in the smaller than 3/8" range. Bark fines of pine, fir or hemlock, are excellent as the primary component of your media. The lignin (it's what makes woody plants woody) contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that too quickly break down to a soup-like consistency. Conifer bark also contains suberin, a lipid sometimes referred to as nature's preservative. Suberin, more scarce as a presence in sapwood products and hardwood bark, dramatically slows the decomposition of conifer bark-based media. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains - it retains its structure.

    Note there is no sand or compost in the media I use. Sand, as most growers think of it, can improve drainage in some cases, but it reduces aeration by filling valuable macro-pores in a medium. Unless sand particle size is fairly uniform and/or larger than about BB size, I leave it out of anything I grow in.
    Compost is too fine and unstable for me to consider using in any significant volume as well. The small amount of micro-nutrients it supplies can easily be delivered by one or more of a number of chemical or organic sources that do not detract from drainage/ aeration.

    The basic blends I use:

    The 5:1:1 mix:

    See dry 5:1:1 mix in the center below. The bark products at 3, 6, and 9 o'clock are ideal for the 5:1:1 mix. The bark at top/ below is prescreened fir bark in 1/8 - 1/4", and what I use for the gritty mix.

    5 parts pine bark fines, dust - 3/8 (size is important)

    1 part sphagnum peat (not reed or sedge peat, please)

    1-2 parts perlite (coarse or all-purpose, if you can get it – not super-coarse)

    garden lime

    controlled release fertilizer (if preferred)

    Big batch:

    2-3 cu ft pine bark fines

    5 gallons peat

    5 gallons perlite

    2 cups dolomitic (garden) lime

    2 cups CRF (if preferred)

    Small batch:

    3 gallons pine bark

    1/2 gallon peat

    1/2 gallon perlite

    4 tbsp lime (or gypsum in some cases)

    1/4 cup CRF (if preferred)

    ~ continued in text box below ~

  • tapla
    Original Author
    last month
    last modified: last month

    ~ page 3 ~

    I have seen advice that some highly organic (practically speaking - almost all container media are highly organic) container media are productive for up to 5 years or more. I disagree and will explain why if there is interest. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will long outlast any peat/ coir/ compost based medium) you should only expect a maximum of two to three years life before a repot is in order. Usually perennials, including trees (they're perennials too) should be repotted more frequently to insure they can grow at as close to their genetic potential (within the limits of other cultural factors) as possible. If a medium which will retain its structure for long periods is desired, we need to look more to inorganic components. Some examples are crushed granite, fine stone, VERY coarse sand (see above - usually no smaller than BB size in containers, please), Haydite, lava rock (pumice), Turface, calcined DE, and others.

    For long term (especially woody) plantings and houseplants, I use a superb medium which is extremely durable and structurally sound. The basic mix is equal parts of screened pine bark, Turface, and crushed granite.

    The gritty mix:


    1 part uncomposted/ screened pine or fir bark (1/8-1/4")

    1 part screened Turface

    1 part crushed Gran-I-Grit (grower size) or #2 cherrystone (screen dust out)

    1 Tbsp gypsum per gallon of medium (eliminate if your fertilizer contains Ca)

    CRF (if desired)

    I use 1/8 -1/4 tsp Epsom salts (MgSO4) per gallon of fertilizer solution when I fertilize if the fertilizer does not contain Mg (check your fertilizer - if it is soluble, it probably does not contain Ca or Mg. If you choose to use my currently favored fertilizer (I use it on everything), Dyna-Gro's Foliage-Pro in the 9-3-6 formulation - no need to use gypsum or Epsom salts in the fertilizer solution.

    The ingredient screens I use when needed:




    If there is interest, you can search for 20-some other threads on the same topic that reached the maxim number of posts allowed.

    If you feel you were benefited by having read this offering, you might also find this thread about Fertilizing Containerized Plants helpful.

    If you do find yourself using media you feel are too water-retentive, you'll find some Help Dealing with Water Retentive Soils by following this embedded link.

    If you happen to be at all curious about How Plant Growth is Limited, please follow the link.

    Finally, if you are primarily into houseplants, you can find an OVERVIEW of the BASICS, which should provide help in avoiding the most common pitfalls encountered by houseplant/ container growers.

    As always - best luck. Good growing!! Let me know if you think there is anything you think I might be able to help you with.


    If you have found value in my effort and feel like saying 'thanks', please consider clicking on my user name that appears at the top of all my posts (tapla Original Author), then click the "Follow" button. I would appreciate it. The reason I ask relates to the idea that an increase in the number of people following someone helps to solidify their 'credibility'. It follows that as their perceived credibility increases, the more likely it is they will be able to help others help themselves. I'm not looking for fame or fortune; rather, I try to help because I've found I can quickly summarize the most important things I've learned over the last 30 years, saving folks a LOT of time/effort. Feeling like I've made a positive contribution to someone's growing experience or growth as a gardener is a reward in itself, and over time has become a natural extension of my own growing experience.

    Al

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    Q

    Comments (150)
    Hi Al, With all the ingredients in hand, I've started the sifting process and had a few questions. I'm trying to swap out 50 containers worth of soil so I'd prefer to do this in the most efficient way. I am using a 9x9 hardware cloth (.088" openings) to filter the fines. Here are the three ingredients I was able to source: 1) Shasta: Orchid Fir Bark: (1/8" - 1/4") http://shastabark.com/products.htm 2) Turface MVP 3) 1/8" Crushed Granite (Desert Gold) http://www.lyngsogarden.com/index.cfm?event=Display.Home.Product.Group&homeCategory=STONE&categoryid=1094&productgroup=PEBCOB&groupname=Pebbles%252C%2520Cobbles%2520%2526%2520%2520Colored%2520Gravel Questions: 1) It seems like it takes a decent amount of time to screen out the fines for one container. I also have constructed two other screens to be used to filter out the larger particles (a 1/4" for the large fir bark and a 9x9 (.1387") for the larger turface/granite). I'm assuming that at the end of the day it is more important to screen out the fines then to screen out the few larger pieces which may be in the mix. Would this be correct? I'm just trying to save some time and there doesn't seem to be that many larger pieces in the mixes. 2) Do you usually rinse out the mixes before you combine them? Does this help get additional dust/fines out? 3) What do you do with all the fines/dust that you sift out? If you are screening out larger pieces what do you with them? Thanks so much in advance. Your advice and guidance have been invaluable. Best, Kernul1
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    Container Soils - Water Movement & Retention XIII

    Q

    Comments (152)
    Hello Al - thanks again for all of your posts and the fruits of your research. I am growing four heirloom tomato plants in containers using your 5-1-1 mix. Here in Raleigh the closest thing I could find to pine bark fines was a product by Timberline called "Soil Conditioner" which seems to be close to the ideal size. But I wanted to ask you two questions, which I hope you have the time to answer (and patience, if you've already answered them - I looked and could not find your thoughts on these): 1. I used a run of the mill mulch to top off my 5-1-1 mixes in the pots and to my dismay discovered the mulch was full of fungus gnats. I will try Gnatrol to get rid of them, but it brings up my question - what do you use for mulch for the 5-1-1? Maybe pine bark nuggets instead of this buggy shredded hardwood I'm using? (large size might help to avoid insect eggs or other stuff hiding inside?) Or do you not mulch? 2. And secondly, what do you use for day to day pest control? I'm spraying insecticidal soap almost daily to kill the whiteflies/thrips/aphids that I see on the leaves but I wonder if there's anything better I can do instead of using the toxic stuff (Sevin, etc). Thanks!
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  • RoseMe SD
    last month

    Yes I did read all three! 👀 Although this post is about container water principles it gives me hope that when/if I decide to plant potted tree to ground, our heavily river-rock filled ground soil won't guarantee a death for the tree!


    Do you have a thread on "transplant shock" you can share? Is the shock more.due to poorly arranged new environment, or to the frail soul of the plant roots?

  • litterbuggy (z7b, Utah)
    last month

    Al, FYI, the link to your user page leads to a Page Not Found notice, but clicking on your user name at the top of the post works fine.

    tapla thanked litterbuggy (z7b, Utah)
  • tapla
    Original Author
    last month

    Do you have a thread on "transplant shock" you can share? Is the shock more.due to poorly arranged new environment, or to the frail soul of the plant roots? At some point, we all harbored a dread of disturbing or damaging the roots of or plants for fear it would do calamitous damage with a visit from the grim reaper immediately subsequent. The truth is, roots are very forgiving of most of the indignity we might choose to heap on them, so long as we are actually ready to perform the root work and use good judgment. A key element of repotting all common houseplants save succulents/ cacti is keeping the roots wet for the entire duration of the repotting session. I'm pretty sure I've provided you links that will go into more detail about how to proceed with the work and what results should look like. Again, you don't need to be as aggressive as I am about repotting. The appearance of the root systems of trees destined to become bonsai specimens is critically important to the appearance of the composition. Flat roots that radiate evenly and outward from the trunk are highly desirable for bonsai. A hobby grower can remain unconcerned about the appearance of the surface roots and trunk flair, so you needn't spend time/ effort at developing flat root systems. Notice how evenly the roots are spaced and how they radiate outward on this maple:


    This tree has been layered off of it's original roots. See the thick wire in both images. That is a tourniquet, the job of which is to provide a 'dam' which blocks the downward flow of nutrients and a growth regulator (auxin) to the old root system.

    Here is another tree (Korean hornbeam) on which I'm setting up a layer because it's roots are so unattractive:


    As occurred with the maple above, the new root system will grow from the circular holes above the plastic zip ties. When the new roots have grown to a suitable stage of maturity, I will cut through the trunk just below the ring of holes, which will be treated with an insoluble rooting aid. Actually, this is an old image and the work of re building the root system has already been successfully completed.

    So, the only time roots can be considered "frail" is when the plant is struggling due to cultural stress or injury or disease pathogens. Root regeneration requires a good deal of energy. If the plant's energy reserves are near nil and conditions are such that the plant is unable to make enough food/ energy to rebuild the root system, it wouldn't bode well for the plant. Ideally, we should complete the regular repotting required to keep plants at the peak of vitality before they decline so far they need to be snatched back from the edge of oblivion.

    I'm not sure there IS such a thing as transplant shock. If there is, it is related to the damage roots sustain during transplanting. If you buy a plant which has been growing under 50% shade cloth and transplant it into the landscape in a full sun site, only to have it burn, you can't consider that or similar errors to be TS.

    If the grower transplants correctly by bare-rooting, correcting problem roots, and back-filling the hole with native soil, there will be a considerable amount of damage to roots, which is why it's best to transplant while trees are in a predictive dormant state if possible. When root damage occurs, growth predictably stalls until the root damage is repaired and the plant's chemical messengers tell plant central the root system has recovered and is now ready to provide for a larger foliage mass.

    Al

  • tapla
    Original Author
    last month

    Thanks LB. I changed it.

    Al

  • a1an
    10 days ago
    last modified: 9 days ago

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


    tapla thanked a1an
  • tapla
    Original Author
    9 days 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
    6 days ago
    last modified: 6 days 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
  • Gregório Miranda
    3 days ago
    last modified: 3 days 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
    2 days ago

    What about the NPK %s?

    Al

  • Gregório Miranda
    2 days 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
    2 days 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
    2 days 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
    2 days ago

    Looks like your efforts paid off. Strong work!

    Al

  • Gregório Miranda
    2 days ago

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

  • tapla
    Original Author
    2 days 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
    3 hours 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
  • tapla
    Original Author
    3 hours ago

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