We often discuss how wicking can affect hydrology in a container, and there are many ways to discourage excess water retention via wicking, but if wicking is a part of the growing strategy, it should be a part of the qualifications surrounding the contention that a particular medium/plant/planting isn't affected by or doesn't support perched water.

Al

I wanted to infer that they were getting the wicking action without knowing it.

Side note :I was seeing people growing in wicking beds, Rain Gutter System by Larry Hall, etc. Even Walmart Bags ( Grow Bags) in a Kiddie Pools. getting very good results. The Results were comparable to standard Container with Wicking, with healthy Root systems. I not sure what containers many of forum members are using, Have had good results with Terra Cotta or Net Pots, Grow Bags, and other Air Pruning Containers. Maybe this this allows more Air than convention Plastic Pots, minimizing some the PWT effects ( wicking and Container Wall permeability).

If anyone has articles or studies on PWT's and their effects on growth, It would be greatly appreciated. I have only been able to find the same information repeated on all sites. The articles repeatedly state Containers create PWT's, PWT height depends on particle size, and deeper containers have less volume affected by PWT's, etc. Thanks

I'm not sure you can say that 'containers create PWTs' w/o qualifying the statement because PWTs also exist in the earth's mineral soils (e.g. in clay soils resting on gravel deposits) and container media can be constructed such that they hold no perched water, regardless of the size/shape of the container. PWT ht does depend on particle size (primarily), but on other less affecting factors as well (like temperature & elevation). Deeper containers do have a higher % of soil that won't support perched water, but that doesn't make plants immune to the direct effects of perched water, or to the secondary effects - even if roots haven't reached an extant PWT.

Al

Just a choice of words :-) Sometimes they refer to The Container Effect.

Got it. I figured that's what you meant, but I knew the OP probably wouldn't know ..... Lol - he's probably confused enough as it is. Have a good weekend. Snowing like crazzy here.

Al

Probably the most accurate way I can think to put it, so it's understandable to me and my own situation is... different materials can cause perched water.

Perched water tables tend to happen more often in containerized situations because of industry standards, because of the materials offered and normally used... or because we take inaccurate information at face value, as in adding a 'drainage layer to the bottom of the pot', which is just a fallacy that's been around forever, though no one really knows why.

As general consumers, we never really stop to think about what happens under the medium within a pot or how it affects a plant; we're all about the plant, itself. We don't take into consideration that anything negative that happens to the roots can take some time to show up in the plant, itself... and by then, it's sometimes too late to save the plant.

We're not born gardeners; it's not an inherent trait. There is no such thing as a "green thumb"... it's all knowledge. But having truly knowledgeable consumers wouldn't serve the industry. The gardening industry in general thrives on profit.

Since I don't have my own profit margin to spend, to give to that industry, to me gaining that knowledge and understanding of exactly what it is roots require and what their functions are, and the little bit of science attached that I've learned is very important. Learning about the various limitations of growing plants in pots has saved me from having to spend money I don't have, and still maintain the joy of being able to grow plants in pots fairly close to optimum... if I can remove a majority of limitations, one of those being perched water.

Okay, I went a little off on a tangent... but looking at how the gardening industry relates to the situation might be thought of as another limitation, no?

Dale, I have tried to share my experiences growing in large containers using potting mix in place of the peat. I do not like peat except for sphagnum which I use sparingly for my orchids and some moisture loving 'dirt' plants.

I agree that large containers grown outdoors on the ground or patio, decks, etc drain out of the pot. I have had potted plants grow their roots out of the pots into the ground. I just moved two trees which are growing in large containers and they sent their roots out into the soil below. The roots were thick and I could not move the pots without help and a saw. No PWT there, or if there was, the ground acted as the wick.

I grew many trees on my deck in NY over summer. Plumerias, Ficus, Citrus and none showed any sign of root problem when repotted. Their roots circled the bottom of the pots.But they were sitting on a deck, 20ft in the air!

My thinking is that when growing small plants such as bonsai, their roots are very limited by pruning. Grown in very shallow containers, any perched water would be extremely detrimental to the plant. If the plant is growing in a 2-3inch pot, one inch of perched water would be very dangerous unless sitting on benches where they could freely drain.

I find your questions interesting and intriguing. I am not arguing with the premise of PWT, but have not had a problem with it in my large container plants nor small plants growing on benches. I do use potting mix as my peat substitute which I like better than peat. It helps the wood chips to hold more moisture. But it is also very adjustable. When I grow a plant I want to drain quickly and hold little moisture, I reduce the amount of potting mix.

I really am not discounting the 'scientific information', just what I have found worked for me under my growing conditions. I have not had any root limitation that I could observe nor growth issues. I'm happy with my results.I am a firm believer in an 'all around growing method.' This includes good light, knowledge of the plant you are growing, temperatures, air movement and correct watering. I have found most folks have plants underlit and overwatered. I try to teach a holistic method of growing.

Three year old Bat Plant which I repotted in Spring. Sitting on a saucer for 3 years and roots were totally encircled at the bottom of the pot. It was bumped up to a 18 gal container.

This Christmas Cactus is over 10 years (can't remember). I moved it with me from NY. It has grown in potting mix and orchid bark its entire life. I have shared pieces of this plant with many friends and family. I repotted every 3 years and saw no sign of root problems. It grew on a table on a saucer for its entire life. If there was PWT I did not see it nor was its growth limited.

This is my ficus before getting repotted and pruned. Looks scraggly but is over 15 years old. Was a little bit of a thing when I bought it. I kept it in the same container and would root prune and put it back in the same pot. It spent the winter in the house sitting on a saucer. Was always terribly root bound and a job to root prune.

This is just a few photos of many container plants I grew without showing root problems. If they were experiencing them, I wasn't aware and was happy with the growth I did get. Only so much you can expect growing indoors.

Sorry for such a long post.

Jane

jane- looks like good results. The variables using bark and wood chips is the variability of quality. The source, age of bark, and possible toxins in fresh bark etc. Fresh Bark and wood will have a Nitrogen draw, usually compensated for with extra N in the feeding. I know Mittlieder Method gardeners use Sawdust and Sand as medium. All wood products should well composted, and tested with a quick growing annual plant, before using. I prefer to keep bark, and wood as mulches, Let Fungi and Free N fixing Bacteria work on it, releasing nutrients to plants. The longevity of each is different in mixes.

Edit: Bark will have more nutrients than wood. But wood does contain some minerals. The term Potash came from residue of burning wood, and wood-ashes have been used for years.

I use orchid bark and buy it in bulk as I grow orchids. I am able to buy various sizes of bark in bulk sizes. I use the bark in my potting mixes but as I've said, mix potting soil (for moisture) and perlite. Depending on the plant and size of container, I adjust the ratio.

I would never recommend fresh wood chips for anything except compost.

Jane

You must realize that when you use the term "woods chips" or recommend people use "wood chips", no one can properly discern your meaning, which means the vagary has the potential to limit or harm the growing experience of others? Why not be clear in your meaning to avoid misunderstanding?

Al

Oh a PWT table can be a huge problem. With my climate here in NZ I really had issues. Almost gave it up at one stage. Then I discovered this fantastic forum and a new world opened up to me. When i started using 5.1.1 and gritty I got the most out of my plants.

To me its as simple as this...A soggy soil contains very little or no oxygen. Roots stagnates in that environment. Most plants don't die, but they sure don't flourish to their genetic potential. They are to busy compromising to reach their potential... Most people in good climates don't even notice the difference, but in a different climate, it becomes a real issue.

I agree Fred. No plant can grow well in a soggy mix.Certainly something I wouldn't want nor recommend. Death sentence for any plant.

The mixture I use drains freely, but keeps enough moisture in the bark to allow time between watering.

Growing in zone 10, watering becomes daily or even more frequent without some moisture retention in the mix. Orchids growing in rock or baskets can be watered every few hours during the heat of summer.

Growing in NY during winter would cause the potting mixes to dry out quickly due to very low humidity.

halocline(5b - CO)

A** kissing time!!

I thought "Jane" was out of the Orchid scene. - "They are destroying
all my orchid buds and flowers. I have tried various methods to rid them
but they are winning. I'm so sick of dealing with them I will not buy
anymore orchids." -Jane.

Yes, halocline I was talking about a thrip infestation (insect) affecting the flower buds on my orchids. Would be more helpful if you posted my entire statement so it would be clear. I am having a terrible time dealing with thrips and getting very frustrated.

Thrips do not affect my 'dirt' container plants. They attack orchid buds.

Jane

"The mixture I use drains freely, but keeps enough moisture in the bark to allow time between watering." Let's examine the term "drains freely". What does that mean? Does it mean that water passes through it fairly quickly and exits the drain hole soon after water is applied? Almost any medium can be said to "drain freely" if that is the standard by which the soil is judged. We know that fine play sand "drains freely", but we also know that growing in it is very difficult to impossible due to the ht of the PWT and accompanying lack of aeration. How much water is left in a medium after it has been saturated and has just stopped draining (container capacity) is a VERY important consideration when assessing how freely a soil drains. For instance, a soil that supports 0-1" of perched water drains much more freely than a soil that supports 6" of perched water, or more.

So what does it take for a mix to be "not soggy"? Will 6" of perched water fit within the "not soggy" parameters? 4"? 3"? Can we agree that, setting the grower's convenience aside, a medium that supports 0-1" of perched water offers the plant better opportunity to realize a greater measure of it's genetic potential than a medium that has, say 4-6" of perched water? So we don't get hung up on how many inches of PW someone's soil might hold, can we agree that from the perspective of plant vitality, less perched water is better?

How much time is enough time between waterings? A week? 2 weeks? 3? I wouldn't grow in a medium that allows a week long interval between waterings because I know with certainty that I'd be leaving a LOT of potential lying on the table. When we purposely construct our soils so they have a built-in reservoir of free water devoid of air in order to increase watering intervals, surely we can't be faulted for thinking there are limitations imposed by the total immersion of roots in anoxic conditions for extended periods, and the longer these periods last, the greater the limitations.

When someone says "I let my plants go for quite a while without watering. Sometimes weeks", and also suggests, "..... it hasn't affected their health nor growth", I immediately think to myself there is a disconnect here because it simultaneously embraces two conflicting beliefs.

Al

Al, I get where you are going.

My container plants grow outdoors. They get watered by rain and by hand. I water by hand when I see they are bone dry. I am not an 'over-waterer'. Small plants 4-8" pots dry out quickly. They are exposed to constant breezes/wind and sun. My larger container plants also dry out but not as quickly, I grow those in large plastic pots. I do not know if they have perched water. If so, it is not affecting the mix drying out. I never water without sticking my fingers deep in the pot. Usually, I notice some wilting with some, and it reminds me to water.

My very large plants let me know they are bone dry because the wind will blow them over. Not a great way to judge but unfortunately, it has happened. I know this will cause a stir, but it is the truth. Hasn't seemed to bother their growth.

When I say the mix drains quickly, I mean when I water by hand, the water pours out the bottom quickly. I have to continue to repeat watering until I see the mix begin to stay damp and hold moisture. With the largest trees, This can take about 3-4 gallons of water. Most lost to the ground. Those trees can then wait a week or longer, depending on the weather.

If rain is predicted (which isn't often in fall/winter) I wait to water and measure how much rainfall we got. During the rainy season (summer), I rarely water by hand. We get heavy thunderstorms almost daily starting in May through August.

My orchids grow in baskets on benches or trees. They drain quickly and dry out quickly. They can go for weeks between watering, depending on the species.

Hope this helps clarify.

Jane

Jane,

Based on your clarification it seems like you aren't in a position to say whether or not perched water is in your pots and/or affecting their growth. The growth you get is acceptable to you, which in the end is all that matters.

You can't "see" that a rootball is dry or wet, and in a larger pot (not sure how you define that Jane), a finger isn't going to do it unless your finger is much longer than mine.

Water that pours out the bottom provides no evidence that the actual roots/rootball has become saturated (compacted soil, as an example), and also provides no information about whether there is perched water in the container.

So if you see Al's point (and I don't think you do), you might have said "You're right - perhaps I am leaving some growth on the table, but, I'm happy with what I see and the level of effort I use to get these results" - and this, of course, is a tradeoff every grower gets to make. No one would argue with you. This thread could fade into obscurity. Every grower gets to decide this balance, and we want to put the decision into the grower's hands, rather than fate's.

BUT,

that is very different than what you actually keep saying, starting with the very first response to this thread, which seems to be continued in your post directly above: "I don't worry about it. Never seemed to be a problem."

Daniel

People vary in their willingness to compromise. Nature does not. She is steadfast, demanding that for plants to realize their full potential, they must be grown absent limitation. When we introduce a limiting factor or increase the impact of a factor already limiting, it's certain nature will unfailingly exact its toll; so, when the grower demands 1-2-3 week or longer intervals between waterings, it's the vitality of our plantings that hangs in the balance.

Al

Another issue frequently left off the table, here, is that not everyone grows in the same climate or environment, so we can't make one opinion a statement that fits all... it's an impossibility. Plants grown in Florida, for example, will encounter different limitations than plants grown in, say, North Dakota... or Wisconsin... or even Arizona.

Fred mentions how picking up a little more knowledge and applying different tactics has helped him to conquer the limitations his climate and environment place upon his growing. I've done the same, and it's helped immensely.

Some people are unwilling to take convenience off the table... and that's fine. It's their decision. But they have to understand that with convenience comes sacrifice of optimal genetic growth potential. That much should be obvious within the confines of this discussion.

If it's not obvious, it points to that person not having read the information provided, or even giving the concepts discussed therein a try.

It's very easy to argue opinions and personal experiences... but physics are what they are; they are unchanging laws. It would be like trying to argue that gravity on Earth doesn't exist. We know it does. It's an unchanging law.

Very interesting discussion. To the OP, a viola is an annual, so it will only live for one season. During that time, it's roots will go nowhere near the bottom of a 3 foot tall pot, so don't worry. If you put a shrub or small tree in the pot, PWT could cause root rot.

As to my gardening practices, I use the same mix throughout my containers to avoid a PWT. The photos of beautiful plants are enjoyable to look at, but don't really prove anything because there are so many factors involved in plant health.

"Usually, I notice some wilting with some, and it reminds me to water".

One thing I will add..I will NEVER ever let my plants go to the point of wilt,never, not even an orchid...I am not sure if anyone knows this, but undue stress on plants like that can cause thrip, mite and mealy populations to stressed plants.....I can't tell you how many plants I have lost because of this..Why put my plants through that kind of stress when I can avoid it all together by not having to worry about a' PWT' drying out? Better to prevent it all together right and use a mix in which one does not have to worry about it?

Jane, beautiful Christmas Cactus........

I totally agree with you Mike. Plants should never wilt. Orchids do not wilt as they have water tanks and have evolved to survive dry periods. But my 'dirt' plants will wilt and I always feel bad. Today I noticed two plants totally wilted. The lack of rain and constant wind dry them out quickly. I take total responsibility for my neglect. They perked up after a good watering but I do not like to do that and is not my practice. Life happens :((

Daniel --""""So if you see Al's point (and I don't think you do), you might have said
"You're right - perhaps I am leaving some growth on the table, but, I'm
happy with what I see and the level of effort I use to get these
results" - and this, of course, is a tradeoff every grower gets to make.
No one would argue with you. This thread could fade into obscurity.
Every grower gets to decide this balance, and we want to put the
decision into the grower's hands, rather than fate's.""""

I do see Al's point and have no problem with gritty mix. I do not experience poor growth due to PWT. So what where am I 'leaving something on the table?" I am not leaving anything on the table as far as I can see. Isn't that enough? How is that an argument? It is not my reality. Might be yours, but not mine. So we see things differently.

No argument. PWT has not affected my plants.

What I try to offer is an alternative when people cannot nor would not go through the trouble of making the mix. There are many who grow plants but do not have the time, money nor desire to get that involved. Sort of like growing lawns. Some people become obsessed with having the perfect lawn. Others could care less what is growing as long as its green. Maybe a bad analogy but that is what I have found.

Yes, I said Perched Water doesn't matter. I believe that. It hasn't affected my plants as far as I can see. I am happy with the growth, I am pleased with my results. Why would I focus on something that doesn't seem to cause the plant a problem? Is that an argument?

I've had things happen over the 50 years of growing. I explored to find the problem and worked to fix it. No science, just constant growing and fixing. Experience. I believe PWT is a problem with small plants such as bonsai. Makes total sense. But, I don't grow bonsai.

I am more obsessed with my orchids. They are my passion. I have hundreds and have had as many for over 20 years. I show my orchids, I win ribbons. I know plants. I'm not a stupid grower or a new grower. But, before orchids, I grew 'dirt' plants, still do. My large house looked like a woodlands. I made terrible mistakes back in the old days and grew and learned. I grew many outdoor flower beds. Beautiful vegetable gardens. I love to garden.

So, the bottom line I am trying to offer an easier way to deal with large container plants. BTW, I grow petunias, inpatients and other annuals in my large container plants. My containers are very large. Some a bit smaller but most over 20 gallons. Annuals grow very well as a top dressing to a large container plant. Are totally unaffected by PWT their roots are not anywhere near the bottom of the large pots. Its lovely. Beautiful, colorful. The OP shouldn't be afraid to grow violas in a large container. Mine actually seed and I get petunias coming back. The trick is to keep them watered, as the surface soil dries out faster than the lower part of the container.

So, Daniel, I stand by what I said to the OP. It is totally true in my life... 'Has never been a problem. '

Lets let this thread end. No sense going back and forth. I stand by everything i write. I am honest, truthful and not playing any sort of game. I'm certainly not arguing with anyone. People can choose what they do. That's what a forum is about.

Lets be fair to each other.

Jane

"I am trying to offer an easier way to deal with large container plants." I think we're all still waiting to learn how it's easier OR better to mix 1 part each of pine bark potting soil and perlite than 5 parts of pine bark and one part each of potting soil (or peat) and perlite. I just don't see the 'easier part of that, Jane. It seems like they take equal amounts of effort, and the medium with the greater fraction of pine bark is both less expensive and holds much less perched water. "BTW, I grow petunias, inpatients and other annuals in my large container plants. My containers are very large. Some a bit smaller but most over 20 gallons." How on earth do you handle a 20 gallon pot? Any pictures? To move a 20 gallon pot under cover (into garage), I had to use a plank to roll it up onto a nursery cart, then pull it into the garage on the cart, then unload it off the cart using the same plank ...... and I had to use 2 cement blocks as counterweights on the front of the cart to keep it from tipping up in the air as I loaded it .... and the pot had an over-turned 5 gallon pail in the bottom as ballast; plus, I was using the very light 5:1:1 mix in it. "Annuals grow very well as a top dressing to a large container plant. Are totally unaffected by PWT their roots are not anywhere near the bottom of the large pots." Oh my! All my annual mixed display containers (and I've grown many hundreds of them) ALWAYS fill the pots with roots - completely and compactly without fail by summer's end. I can't remember the last time I had a pot with annuals that didn't get so jam packed full of roots that the whole soil mass lifted right out of the pot as a single unit with hardly a crumb of soil falling off of the root/soil mass. I actually never have to clean ANY soil off the inside of my mixed container or tomato/pepper pots because ALL of the soil comes out of the pot with the roots - even the VERY large containers - almost like they'd been scrubbed clean. My experience is completely different than yours - I wonder if it could be the difference in the soils we use?

Al

Why mince words. The real difference in experience is the crux of this thread.

PWT affects any container where it exists, and it most likely exists in a significant fashion in any container not explicitly designed to minimize PWT.

Jane,

I find it telling that though you are 100% sure that PWT doesn't effect you and your large containers of "dirt plants" - based not on science or fact but only on your own observations - you simultaneously believe that it is an issue for Bonsai, which you freely admit you have no experience with. This makes as little sense as your denial of physics and science.

Daniel

On one hand, you have people who always make sure science and logic are in their corner so discussions like this might be avoided. On the other hand, you have a person who abhors anything scientific or technical, but who insists on offering conclusions that cannot be arrived at w/o understanding the scientific principles that support or disprove the observations. If we can't use science to explain OR validate the statements we make up to fit what we think we're seeing, our statements are uneducated guesswork - nothing more.

I know with certainty that even a well-made 5:1:1 mix (which would be made with a 15% fraction of peat or potting soil + whatever bark fines there are in the bark product) supports SOME perched water, all of which is limiting ..... and I freely admit that fact (even though at a 15% fraction of the whole it's much LESS limiting than media with much larger fractions of peat or potting soil. How is it then that plants in Jane's 1:1:1 mix of pine bark, potting soil and perlite, which has more than twice the volume of fines than the 5:1:1 mix, are absolutely not limited by the impact of perched water (when her choice of container media supports more than twice the volume of perched water as the 5:1:1)? That's where the disconnect (cognitive dissonance) lies.

Al

How is it then that plants in Jane's 1:1:1 mix of pine bark, potting soil and perlite, which has more than twice the volume of fines than the 5:1:1 mix, are absolutely not limited by the impact of perched water (when her choice of container media supports more than twice the volume of perched water as the 5:1:1)?

How ?? is easy Simply let Jane water her plants the way she wants and when or if they should become pwt ( water unhealthy/ or killed) then she may or may not consider some of the ideas from others

As this is an argument... or more accurately, an attack on Al's teachings... closing in on a decade, it is highly doubtful that the only poster speaking without science and physics, or offering any sort of explained methodology, will ever concede that her plants are in any way compromised by perched water and not reaching their optimum genetic growth potential.

That's it in a nutshell.

From a logical standpoint, it is not reasonable to bend and twist idealism and fallacy, while leaving facts out of the equation, to arrive at or fit a specific agenda... as is done every day within the realm of politics.

Can I leave plants sitting in water?

Found Interesting Paper from Purdue University.

Can I leave plants sitting in water?

sidenote:

In thinking about water saturated areas in a growing
medium. All smaller pores and micro channels in a growing mix are 100% saturated
after irrigation. It seems the mediums are a mixture of saturated and unsaturated
zones anyway. One possibility for
excellent aeration and water holding mixes, is to use only large particles with
excellent internal water holding properties. Similar to ground up pieces of
sponge in principal. Providing water in internal pores, and air in all inter-particle
spaces. Similar to pellitized Peat moss.

"One possibility for excellent aeration and water holding mixes, is to use only large particles with excellent internal water holding properties." This is the concept on which the gritty mix is based, and its water retention is adjustable by varying the ratio of internally porous: non internally porous components.

Al

"One possibility for excellent aeration and water holding mixes, is to use only large particles with excellent internal water holding properties." Your Correct. I see your point on the Gritty Mix Concept. Gritty mix uses the Bark ( medium water source) and Calcined Clay(limited amount) as a water source. I was referring to much higher moisture storage substance(like Rockwool), with more Plant Available Water (super pellets). Plus eliminating the Total Porosity limiting grit faction in mixes. A more idealized growing medium in theory only.

"Can I leave plants sitting in water?"

You can if you're Jane!!

Rob

"You can if you're Jane!!"

Halocline, I'm sure you are not referencing me! My plants do not sit in water. Must be another Jane....

Jane

HA!

Ha Ha funny you two ;-)

Thought this would be interesting. I repotted my Pachira last July. I've had this tree since a small baby plant. In July I took off over 1/3 of the root system. There are three trees in the pot. They were originally braided.

In six months the tree has doubled in size. It will get a hard chop this spring as it has grown to the screen roof. I hang orchids on the trees and have discovered by bending the trunks, I get back budding. I gradually add weight to the trunks.

Absolutely beautiful, and has responded to the repot by great growth. Its a beautiful tree.

Jane

Tapla- how would you suggest fixing a perched water table in an existing raised garden bed? I made the mistake of not adequately mixing the native soil with the soil mix and had terrible drainage last year. Since I havent planted yet, now would be the time to make changes.

What type of soil underlies the bed?

Al

I know this is not scientific, but it is the typical new england soil (not sandy or clay) with a lot of intermittent rocks.

Unless your bed is in a large depression that water tends to flow into, the only reason you should have a PWT in your raised bed soil is if there is a significant disparity in particle size between what's in the bed and your native soil. Water only perches in soils that have a substrata with a particle size larger than 2.1x that of the material that makes up the top layer.

Even if your bed is built on extremely fine clay that all but prevents percolation, you should still have no serious issues for the first few years. Let's say you do have a PWT in your RB. As the top of the soil surrounding the bed dries, it's capillarity should pull water horizontally from the raised bed. Again, the only time this won't occur is when the surrounding soil is at least 2.1x larger in particle size than what's in the bed.

Raised beds over clay become increasingly problematic with time. As soil life moves OM from the RB into the soil below, it increases porosity. Lateral hydraulic pressure then causes the newly made air pores, that would normally be considered a good thing, to fill with water every time it rains. Ideally, RBs intended for long term use should be tiled so water can be moved away passively, tiled to a sump that can be pumped out, or tiled to a French drain, which often works fine when it's not really needed and fails when it is. French drains are fine if they are tiled so the water can run downhill away from your RBs. You can also dig ditches around your RBs. The same lateral hydraulic pressure that fills pores of disturbed earth beneath your beds will fill the ditches. Here too, you would need to have the ditches configured to passively direct water downhill away from the site, or to a sump you can pump when required.

What I'm left wondering now is, how can it be that the soil is so fine it CAN hold perched water. What is the make-up of the soil in your RBs?

Al

I used Miracle-Gro raised bed soil mix, which seemed like a better idea than plain planting soil that everyone on here says not to use. The issue is I would stick my finger down 8" and the soil was consistently cool and damp, even during the height of summer. Terrible for peppers.

I had thought about adding perlite or vermiculie to loosen the soil, but I think I read on here that it would not do much good.

Dig down and grab a handful of soil about an hour after you water. Squeeze it. If you can squeeze water out of the soil, you need to amend it. Vermiculite won't help, but perlite will. Even better than perlite, would be #2 cherrystone or grower size poultry grit. Equal measures of pine bark and perlite would also serve you very well. Pine bark breaks down slowly enough that it won't create a serious N immobilization issue, but you would need to stay on top of the plant's N needs.

My raised bed soil:

Al

Thanks. How do I decide how much Perlite/cherrystone to buy?

How much water can you squeeze out of the soil you grabbed a handful of from 6" below the surface?

Al

Haven't tested yet. We just had a torrential rain storm here and I'm guessing that will skew things. Will check in a few days and report -thanks for your help.

I am seeing this thread for the first time, and while I did not read the whole thing I am wondering if the original question was really addressed. The original poster is talking about situations where the root zone is far away from the perched water table. Instead of addressing that specific issue, somehow this thread got directed to the question of whether perched water table matters at all (clearly it does).

Let's consider a specific example. Say I have an oil vase that is four feet high. I fill that will 511. Then I plant shallow rooted plants in that oil vase, so those roots are about 3.5 feet away from the bottom of the pot.

In this post, a user makes the point that you want the root zone to have less than 5 kPa of pressure/tension in order to be able to take water out of the soil and nourish the roots. I do not understand this issue well, but using the data in that post (i.e., 1 kPa = 3.94 inches for a particular soil mix), that seems to imply that this soil mix would get to 5 kPa at about 20 inches of height from the top of the perched water table. You would get to 5 kPa at: 3.94 in/kPa * 5 kPa = 19.7 in ~= 20 in. That might imply that you want to keep the bottom of your root zone within 20 inches of the top of the PWT, otherwise the roots might have problems getting the best extraction of water out of the soil, in the days after watering.

So back to the original question that was posted, it seems to me that there might be value in looking at the root behavior of what you are planting, and the size of the pot, and you might want to keep the bottom of your roots within an appropriate distance from the top of the PWT, in order to give the roots an easier time in extracting water out of the soil.

That's way more complexity than most of us are willing to deal with, and I am sure there is a lot of science and practical understanding that I do not have on this issue. But maybe it is not a good idea to put a shallow rooted plant into a very deep container.

Unwanted soil gasses like CO2 and methane are also byproducts of soil saturation that can affect root health/function regardless of their proximity to the PWT. Too, roots that alternate between saturation and acceptable air:water soil ratios undergo a cyclic death from inundation followed by root regeneration when air:water ratios return to a favorable level. The energy a plant uses for root regeneration is energy that otherwise would have gone toward increasing the plant's o/a mass or increasing its store of energy in reserve, so there's a heavy toll to be paid for root problems due to inundation.

Very often, the toll is taken in loss of potential. IOW, a plant might appear to be healthy, even though it is suffering a significant loss of potential. It's good to remember that, where plants are concerned, lost potential can never be regained. Once gone, it's gone for good.

Al

Al, can you comment about the duration of inundation required to cause that root death? It is something I have not been able to find any information on. An hour? A day?

Not so much that it will cause root death per se, It's the loss of size, flowering and overall vigor because roots can not form in the first place. Stunted root systems don't produce good plants!

How long it takes depends on factors like what the media is made of, temperature, and what plant we're talking about ...... and anoxic conditions in the rhizosphere does cause root death. The finest roots, the roots that do the lion's share of the work are first to die, followed by increasingly larger roots as inundation continues.

Al

Al - I did a moisture check of the soil. 9" down, the soil was cold (not surprising given its April). When I squeezed the soil in my hand, no water dripped out, but it was damp enough where I could mold the dirt ball and compact it into a ball, like I would with play-dough (not to confuse anyone, this is not clay soil).

My issue with last year is the soil was consistently cold and damp like this. Fine for tomatoes, horrible for peppers.

Hi just- following up. Not sure if you saw this, Al.