jdwhitaker_gw

Container soils and water in containers (cont.)

jdwhitaker
15 years ago

Al's original post has reached the maximum of 150 replies, and I think this discussion should continue. I'll start the new thread with a reprint of Al's (tapla's) treatise on container soils and water, and end with a link to the original thread...


CONTAINER SOILS AND WATER IN CONTAINERS

Posted by tapla z5b-6a MI (My Page) on Sat, Mar 19, 05 at 15:57

The following is very long & will be too boring for some to wade through. Two years ago, some of my posts got people curious & they started to e-mail me about soil problems. The "Water Movement" article is an answer I gave in an e-mail. I saved it and adapted it for my bonsai club newsletter & it was subsequently picked up & used by a number of other clubs. I now give talks on container soils and the physics of water movement in containers to area clubs.

I think, as container gardeners, our first priority is to insure aeration for the life of the soil. Since aeration and drainage are inversely linked to soil particle size, it makes good sense to try to find a soil component with particles larger than peat and that will retain its structure for extended periods. Pine bark fits the bill nicely.

The following hits pretty hard against the futility of using a drainage layer in an attempt to improve drainage. It just doesn't work. All it does is reduce the soil available for root colonization. A wick will remove the saturated layer of soil. It works in reverse of the self-watering pots widely being discussed on this forum now. I have no experience with these growing containers, but understand the principle well.

There are potential problems with wick watering that can be alleviated with certain steps. Watch for yellowing leaves with these pots. If they begin to occur, you need to flush the soil well. It is the first sign of chloride damage.

One of the reasons I posted this is because of the number of soil questions I'm getting in my mail. It will be a convenient source for me to link to. I will soon be in the middle of repotting season & my time here will be reduced, unfortunately, for me. I really enjoy all the friends I've made on these forums. ;o)

Since there are many questions about soils appropriate for containers, I'll post by basic mix in case any would like to try it. It will follow the Water Movement info.

Water Movement in Soils

Consider this if you will:

Soil need fill only a few needs in plant culture. Anchorage - A place for roots to extend, securing the plant and preventing it from toppling. Nutrient Sink - It must retain sufficient nutrients to sustain plant systems. Gas Exchange - It must be sufficiently porous to allow air to the root system. And finally, Water - It must retain water enough in liquid and/or vapor form to sustain plants between waterings. Most plants could be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement of water in soil(s).

There are two forces that cause water movement through soil - one is gravity, the other capillary action. Gravity needs little explanation, but for this writing I would like to note: Gravitational flow potential (GFP) is greater for water at the top of the pot than it is for water at the bottom of the pot. I'll return to that later. Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like soil particles and the sides of the pot. 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, waters bond to itself can be stronger than the bond to the object it might be in contact with; in this condition it forms a drop. Capillary action is 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. It will stop rising when the GFP equals the capillary attraction of the fibers in the paper.

There is, in every pot, what is called a "perched water table" (PWT). This is water that occupies a layer of soil that is always saturated & will not drain at the bottom of the pot. It can evaporate or be used by the plant, but physical forces will not allow it to drain. It is there because the capillary pull of the soil at some point will equal the GFP; therefore, the water does not drain, it is "perched". If we fill five cylinders of varying heights and diameters with the same soil mix and provide each cylinder with a drainage hole, the PWT will be exactly the same height in each container. This is the area of the pot where roots seldom penetrate & where root problems begin due to a lack of aeration. From this we can draw the conclusion that: Tall growing containers are a superior choice over squat containers when using the same soil mix. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding soil above the PWT. Physiology dictates that plants must be able to take in air at the roots in order to complete transpiration and photosynthesis.

A given volume of large soil particles have less overall surface area in comparison to the same volume of small particles and therefore less overall adhesive attraction to water. So, in soils with large particles, GFP more readily overcomes capillary attraction. They drain better. We all know this, but the reason, often unclear, is that the PWT is lower in coarse soils than in fine soils. The key to good drainage is size and uniformity of soil particles. Large particles mixed with small particles will not improve drainage because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential. Water and air cannot occupy the same space at the same time. Contrary to what some hold to be true, sand does not improve drainage. Pumice (aka lava rock), or one of the hi-fired clay products like Turface are good additives which help promote drainage and porosity because of their irregular shape.

Now to the main point: When we use a coarse drainage layer under our soil, it does not improve drainage. It does conserve on the volume of soil required to fill a pot and it makes the pot lighter. When we employ this exercise in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This reduces available soil for roots to colonize, reduces total usable pot space, and limits potential for beneficial gas exchange. Containers with uniform soil particle size from top of container to bottom will yield better drainage and have a lower PWT than containers with 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 make the downward transition because the capillary pull of the soil above the drainage layer is stronger than the GFP. The reason for this is there is far more surface area in the soil for water to be attracted to than there is in the drainage layer.

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 are now employing the pot-in-pot or the pot-in-trench method of growing to capitalize on the science.

If you discover you need to increase drainage, insert a wick into the pot & allow it to extend from the PWT to several inches below the bottom of the pot. This will successfully eliminate the PWT & give your plants much more soil to grow in as well as allow more, much needed air to the roots.

Uniform size particles of fir, hemlock or pine bark are excellent as the primary component of your soils. The lignin 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 rapidly break down to a soup-like consistency. Bark also contains suberin, a lipid sometimes referred to as natureÂs preservative. Suberin is what slows the decomposition of bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains.

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 starve to death because they cannot obtain sufficient air at the root zone for the respiratory or photosynthetic processes.

To confirm the existence of the PWT and the effectiveness of using a wick to remove it, try this experiment: Fill a soft drink cup nearly full of garden soil. Add enough water to fill to the top, being sure all soil is saturated. Punch a drain hole in the bottom of the cup & allow to drain. When the drainage stops, insert a wick several inches up into the drain hole . Take note of how much additional water drains. This is water that occupied the PWT before being drained by the wick. A greatly simplified explanation of what occurs is: The wick "fools" the water into thinking the pot is deeper, so water begins to move downward seeking the "new" bottom of the pot, pulling the rest of the PWT along with it.

Having applied these principles in the culture of my containerized plants, both indoors and out, for many years, the methodology I have adopted has shown to be effective and of great benefit to them. I use many amendments when building my soils, but the basic building process starts with screened bark and perlite. Peat usually plays a very minor role in my container soils because it breaks down rapidly and when it does, it impedes drainage.

My Soil

I'll give two recipes. I usually make big batches.

3 parts pine bark fines

1 part sphagnum peat (not reed or sedge peat)

1-2 parts perlite

garden lime

controlled release fertilizer

micro-nutrient powder (substitute: small amount of good, composted manure

Big batch:

3 cu ft pine bark fines (1 big bag)

5 gallons peat

5 gallons perlite

1 cup lime (you can add more to small portion if needed)

2 cups CRF

1/2 cup micro-nutrient powder or 1 gal composted manure

Small batch:

3 gallons pine bark

1/2 gallon peat

1/2 gallon perlite

handful lime (careful)

1/4 cup CRF

1 tsp micro-nutrient powder or a dash of manure ;o)

I have seen advice that some highly organic soils are productive for up to 5 years. I disagree. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will far outlast any peat based soil) you should only expect a maximum of three years life before a repot is in order. Usually perennials, including trees (they're perennials too, you know ;o)) should be repotted more frequently to insure vigor closer to genetic potential. If a soil is desired that will retain structure for long periods, we need to look to inorganic amendments. Some examples are crushed granite, pea stone, coarse sand (no smaller than BB size in containers, please), Haydite, lava rock, Turface or Schultz soil conditioner.

I hope this starts a good exchange of ideas & opinions so we all can learn.

Al

Comments (150)

  • tapla
    14 years ago
    last modified: 6 years ago

    Readers of this forum have always proven to be quite intelligent, and are surely able to evaluate practical experience and what we have set forth - certainly no need for me to belabor a point. ;o)

    Al

  • justaguy2
    14 years ago
    last modified: 6 years ago

    Agreed.

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  • filix
    14 years ago
    last modified: 6 years ago

    What a great topic. I always wanted to make my own potting soil. Jolly gardner in maine sells 1 cubic foot bags of acadia perenial pine bark mulch for 5.50 per bag. Acualy the sell to nurseries and they sell it for that. They have a web site jollygardner.com Sorry I dont know how to do a link. That stuff sounds like the stuff I need. It is composted. They also sell pine bark mulch that is not composted. If I read correctly Al prefers that? I might try both. Should the perlite I buy be the coarse stuff? And for the Micro N could I just use one gallon of good compost Rather than manure? Also what kind of controled relese F should I buy? I hope these questions were not already covered. Cant wait to do this. Thanks.....

  • tapla
    14 years ago
    last modified: 6 years ago

    I generally prefer partially composted bark in all my short term plantings and uncomposted bark in plantings I don't intend to repot after the initial growth cycle. Roughly translated, this means that I like composted bark for the "pretty stuff" (floral display containers) and uncomposted pine or fir bark for the long term (usually woody plants) that will not be repotted until after the second or possibly third growth cycle, but you certainly needn't be so critical.

    I always use coarse perlite (or medium, if for some reason I cannot locate the coarser product). I'm currently using a 12 month controlled release fertilizer (a German manufacturer) that I got from a wholesale supply house, but any brand will probably work well. The formulation would depend on things like your temperatures, plant material, and what your soil is made of. Soils comprised of uncomposted organic particulates generally require the application of more N, so for those, choose a fertilizer with a higher N content than for soils with partially composted materials in them.

    I avoid garden compost in my soils. There is a difference between composted bark and compost. Composted bark, particularly conifer bark, has a high lignin content and is rich in suberin. Lignin is quite stable, and is what is left of wood after the cellulose is "eaten up". Suberin is a lipid, concentrated in bark, which makes it very difficult for micro-organisms to cleave hydro-carbon chains in organic matter, which additionally adds to bark's stability.

    Compost adds very little to container soils in the way of micro-nutrients. Instead, seek out a fertilizer that contains the minor elements, or use any one of a number of either organic or inorganic supplements. Fish/seaweed emulsions, Earth Juice, STEM, or Micromax (to name a few) are reliable sources of the minors and I much prefer them to pore-clogging garden compost. Since I wrote the article (several years ago) I've also stopped adding any manures to container soils for the same reason (reduces aeration by clogging pores and slows drainage), as well as the fact that you often introduce many unwanted weed seeds in the manure.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    Thanks for such a detailed response. I have learned alot from you already. So I would use composted mulch for my annuals, like morning glorys, moon flowers ect... And uncomposted for clematis, roses, jasmine ect....? Thanks Al....Filix

  • tapla
    14 years ago
    last modified: 6 years ago

    Nothing need be so rigid as that, Filix. I just relate what I have learned & what works best for me. As I relate it, I try to be sure that science supports it and my conclusions are largely free of post hoc fallacy, so common in these forums. Please, draw your own conclusions based on what you observe in your growing efforts, perhaps only using my observations as something of a base from which to begin your own explorations.

    May I suggest that you start by settling on a soil you can replicate consistently and the components of which you can obtain easily and inexpensively? From there, you can easily expand into the area of building soils that are individually suited to a particular planting if you prefer. The basic mix with pine bark, perlite, and peat as the primary components is a good starting point.

    Good luck - and btw, we all learn when you ask questions, myself included. ;o)

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    What do you do with the soil you made for one years use? Can you bring it back somehow. Or just dump it in the compost pile?.....Thanks....Filix

  • tapla
    14 years ago
    last modified: 6 years ago

    There is wide disagreement on this point, but I never reuse it, turning it into the garden or on the compost pile instead. Others reuse it.

    If you use the search words "tapla reuse" on this forum's search function, without the quotation marks, you'll be able to read other's comments about reusing container soils. Here is my opinion:

    In my estimation, the only case to be made for reusing container soils is one of economics, and you'll never find me argue against making that decision. If you can't afford, you can't afford it. That said and setting economics aside, you might decide to reuse soil for reasons other than economical. Perhaps the effort involved with acquiring (or making your own) soil is something you might not wish to go through or be bothered with.
    In any case, it would be difficult to show that soils in a more advanced state of structural collapse can somehow be preferred to a soil that can be counted on to maintain its structure for the entire growth cycle. So, if the economic aspect is set aside, at some point you must decide that "my used soil is good enough" and that you're willing to accept whatever the results of that decision are.

    All soils are not created equal. The soils I grow in are usually pine bark based & collapse structurally at a much slower rate that peat based soils, yet I usually choose to turn them into the garden or give them over to a compost pile where they serve a better purpose than as a container soil after a year of service. Some plantings (like woody materials and some perennials) do pretty well the second year in the same bark-based soil, and with careful watering, I'm usually able to get them through a third year w/o root issues.

    Watering habits are an extremely important part of container gardening. Well structured soils that drain well are much more forgiving and certainly favor success on the part of the more inexperienced gardeners. As soils age, water retention increases and growing becomes increasingly difficult. If your (anyone's) excellence in watering skills allows you to grow in an aging medium, or if your decision that "good enough" is good enough for you, then it's (your decision) is good enough for me, too.

    The phrases "it works for me" or "I've done it this way for years w/o problems" is often offered up as good reason to continue the status quo, but there's not much substance there.

    I'm being called away now, but I'll leave with something I offered in reply on a recent thread:
    "... First, plants really aren't particular about what soil is made of. As long as you're willing to stand over your plant & water every 10 minutes, you can grow most plants perfectly well in a bucket of marbles. Mix a little of the proper fertilizers in the water & you're good to go. The plant has all it needs - water, nutrients, air in the root zone, and something to hold it in place. So, if we can grow in marbles, how can a soil fail?

    Our growing skills fail us more often than our soils fail. We often lack the experience or knowledge to recognize the shortcomings of our soils and to adjust for them. The lower our experience/knowledge levels are, the more nearly perfect should be the soils we grow in, but this is a catch 22 situation because hidden in the inexperience is the inability to even recognize differences between good and bad soil(s).

    Container soils fail when their structure fails. When we select soils with components that break down quickly or that are so small they find their way into and clog macro-pores, we begin our growing attempts under a handicap. I see anecdotes about reusing soils, even recommendations to do it all over these forums. I don't argue with the practice, but I (very) rarely do it, even when growing flowery annuals, meant only for a single season.

    Soils don't break down at an even rate. If you assign a soil a life of two years and imagine that the soil goes from perfect to unusable in that time, it's likely it would be fine for the first year, lose about 25% of its suitability in the first half of the second year, and lose the other 75% in the last half of the second year. This is an approximation & is only meant to illustrate the exponential rate at which soils collapse. Soils that are suitable for only a growing season show a similar rate of decline, but at an accelerated rate. When a used soil is mixed with fresh soil after a growing season, the old soil particles are in or about to begin a period of accelerated decay. I choose to turn them into the garden or they find their way to a compost pile.

    Unless the reasons are economical, I find it difficult to imagine why anyone would add garden soils to container soils. It destroys aeration and usually causes soils to retain too much water for too long. Sand (unless approaching the size of BB's), has the same effect. I don't use compost in soils because of the negative effect on aeration/drainage. The small amount of micro-nutrients provided by compost can be more efficiently added, organically or inorganically, via other vehicles.

    To boil this all down, a container soil fails when the inverse relationship between aeration/drainage goes awry. When aeration is reduced, soggy soil is the result, and trouble is in the making."

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    I had a thought. I have a friend that owns a saw mill. He has mounds of white pine bark, with some hemlock. I own a chipper/shreder. I wonder if I couldn't grind up and sift my own. Are there insects in pine bark that would be a concern? Do the people who sell the stuff do anyhting to it to get read of any insects? I have a pickup truck. Mmmmmm. come on spring....Filix

  • tapla
    14 years ago
    last modified: 6 years ago

    Go for it, but you may wish to avoid slashings that have a considerable amount of sapwood attached to the bark - or bark to sapwood, depending on your perspective.

    Insects that make their home in the bark of living trees would not normally be of particular concern in soils.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    Large particles mixed with small particles will not improve drainage because the smaller particles fit between the large, increasing surface area which increases the capillary action.
    When you buy a bag of pine bark mulch, don't you get both small particles and large? I would like to know because I bought a pickup truck load of pine bark mulch. It is about two months old. I will let it age until may. Then I will sift it through a screen with 1/2 holes. Do you think I should have another finer screen below to let smaller particles pass through. Or is this spliting hairs? Thanks

  • tapla
    14 years ago
    last modified: 6 years ago

    The highly irregular shape and generally larger particulate size of conifer bark mulch tends to improve drainage in spite of the mix of particulate sizes. You can "fine tune" the amount of air held in the media and drainage speed by adding more or less perlite. Here, it's good to remember that any media will break down in size (compact) over time. Peat based mixes break down at a far more rapid rate than bark-based, and soils with a lower organic component at a slower rate than either. This is why I chose to grow long-term plantings (including house plants) in soils that range from 0 to around 40% organic parts.

    If you are screening your soil, I would add what remains above the .5 inch screen to the garden or beds and use what passes through it in your soils. If you feel you have an extremely high % of fines, you could screen it through insect screening & turn what passes through into the garden, but I don't bother with this step for short term plantings, choosing instead to add a little extra perlite if I'm concerned.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    Thanks again Al. Im chomping at the bit to do this.

  • justaguy2
    14 years ago
    last modified: 6 years ago

    Al,

    I think you have done more research on various potting mix ingredients than I have and so I am wondering if you have enough info readily available that you could post something akin to a handy chart regarding the properties of various mediums?

    I am not asking you to do a ton of research, just if you have the info handy.

    For example the turface/profile makers have compared turface/sand mixtures to sand/peat mixtures on golf courses and have statistics regarding drainage rates, water holding capacity, aeration, CEC, etc.

    One can conclude from this that turface holds less water than peat, but has better drainage and aeration. Turface also degrades much more slowly.

    What I would love to see, if you have the info handy, would be a chart comparing various ingredients in terms of longevity (how long they take to degrade into too small a particle size), aeration/gas exchange, water holding capacity and CEC.

    Any other info you consider relevant would be good as well.

    Again, only if you have the info handy, I certainly wouldn't expect you to have to look this stuff up.

    It could be very handy for those trying to choose an 'ideal' mix that best meets the needs of the plant as well as the grower.

  • tapla
    14 years ago
    last modified: 6 years ago

    Gee - while I appreciate your confidence, I already spend a good amount of time answering questions in my e-mail, plus that time that I spend here for the fun of thinking I might make some difference to a few folks. I suppose I should say that while I know how all these materials perform from having used them for many years, I'm not really willing to start building charts & graphs for things that you could easily research on your own.

    Very respectfully, I'll say that if you have a specific question, I'm more than willing to answer it to the best of my ability, or even to go looking for the answer, if I don't know it, but to ask me to start to compile research that is not likely to be used anyway, is asking much.

    If you were a member of the "Container Gardening Club", and you came to me (just pretend I was head of the program committee) with your request. I would say, "Dave (that's your name - right?), I think you have a good idea here. What I think you should do is research this yourself and put it in a form that is understandable and present it to the club at a future meeting. What month would you like to do it? You do know, that the person putting the program together learns more than anyone - right?" ;o)

    Al

  • justaguy2
    14 years ago
    last modified: 6 years ago

    Gee - while I appreciate your confidence, I already spend a good amount of time answering questions in my e-mail, plus that time that I spend here for the fun of thinking I might make some difference to a few folks.

    You do make a difference and your efforts are not wasted. I completely understand your not wishing to undergo the effort of such a compilation. That is why I said 'only if you have the data handy' or something similar.

    In other words if you would have to go hunting around and taking a large amount of time to consolidate the data into hard numbers I would consider it an unreasonable request.

    I just thought that since you have clearly done a lot of homework you might already have the notes handy ;-) I suppose I should say that while I know how all these materials perform from having used them for many years, I'm not really willing to start building charts & graphs for things that you could easily research on your own.

    I totally understand, but at the same time as I read through your posts and Rhizos I see the 2 of you saying the same thing repeatedly, in fact I see that you in particular are obviously saving some of your more detailed posts and then cut/pasting them as replies to repeatedly asked questions.

    This is a good technique to provide the info in a manner that conserves your time. However, building a potting medium that is ideal for both the grower and the plant takes a good deal of knowledge and it seems to me it would be a helpful thing to reference if the various relevant properties of the container media choices were presented in an easy to understand form. Perlite and turface both provide a good amount of air spaces between particles, but turface has more spaces within the particle to hold air and moisture. Turface also has an ionic charge that allows it to retain many nutrients well and perlite does not. Peat and turface both offer somewhat comparable aeration when fresh, but peat rapidly breaks down to hold more water and less air than turface. This kind of thing is what I am talking about. Putting it into a chart form would be a handy reference. Very respectfully, I'll say that if you have a specific question, I'm more than willing to answer it to the best of my ability, or even to go looking for the answer, if I don't know it, but to ask me to start to compile research that is not likely to be used anyway, is asking much.

    I agree, it is asking a lot. If you don't already have the info compiled in a form you could just copy and paste then it is asking way too much, I just thought I would ask if you had already possessed the info in such a form or a form that could be whipped into shape with little additional effort.

    You seem like a geek to me (that's a compliment) so I thought there was a reasonable chance you would have the info in a copy/paste form or close to it. If you were a member of the "Container Gardening Club", and you came to me (just pretend I was head of the program committee) with your request. I would say, "Dave (that's your name - right?)

    Dave? Dave's not here, man. ;-) I think you have a good idea here. What I think you should do is research this yourself and put it in a form that is understandable and present it to the club at a future meeting. What month would you like to do it? You do know, that the person putting the program together learns more than anyone - right?" ;o)

    Nah, too lazy myself. ;-)

    And I certainly do not expect you to do it either.

    I was just asking if you already had the info handy to present in a form that could later be referenced to handle the questions many ask here.

    Plus, I would rather you do the work than me ;-)

  • filix
    14 years ago
    last modified: 6 years ago

    Al what kind of controled release fert. do you use. Im getting all my ducks in a row. I have my pine bark, coarse perlite, peat moss, dolomite lime in granular form[ is that ok]? And now i found c,r.f. What I found comes in pellets That you put near the roots, just one I think. I found scotts micromax. But in a very large bag for around 70 bucks. Does it come any smaller. Hope Im not a pain..filix

  • tapla
    14 years ago
    last modified: 6 years ago

    I use a German import I buy in large bags from a wholesaler, but it's roughly the same as Osmocote 19-6-12.

    Some of the large pelletized products are not controlled release, and even products labeled controlled release are very temperature dependent. please read the product info carefully so you don't over-fertilize,

    Contact me off forum for more info on smaller quantities of Micromax (or STEM), please.

    Al

  • justadncr
    14 years ago
    last modified: 6 years ago

    Well I have spent New Years Eve reading this entire post and enjoyed it more than most of my other years! I do have one question.
    I am wondering what you use for a wick. And do you use the wick to water the plant or drain water out? Thanks for all the info!

  • stressbaby
    14 years ago
    last modified: 6 years ago

    Justadncr,

    I have replicated Tapla's wick experiment using Promix and CHC, and as a wick, I used a thin strip of an old towel...it worked very well. The wick serves to drain the perched water table out of the container.

    As an aside, a nurseryman friend of mine uses wicks in a different way. He inserts a 2-3" piece of 1/4" nylon rope into the center hole of each pot. Then the pots are place on sand beds, large beds with about 6" of sand, covered with landscape fabric, and irrigated with a float/valve system. The pots are placed on the fabric (and ideally never moved again until sold) and the wick draws the water into the pots. Believe it or not, this is sufficient to irrigate hundreds of plants per bed with no overhead watering. Fascinating system.

    SB

  • filix
    14 years ago
    last modified: 6 years ago

    I have learned so much this topic. I read it also last night for the second time. I have a freind who has been gardening for many years. He does alot of window boxes. Every year he plants the same geraniums. Most of the boxes are right under the drip edge of the house. So the plants get way too much water. Half way through the summer the ones under the drip edge look very bad. Those plastic inserts he puts in the window boxes are held up by two 1" pieces of wood. He needs to put alot more holes in them, add a wick and some screen to keep the soil in , and maybe change to al's mix. He uses farfed's mix. [ can't spell]

    Im going to try al's mix in my morning glorys. I have been growing them for many years with some pretty good results. I was always told to just grow them in plan dirt. But im sure they would like some air for their roots. They couldn't have been getting much from just top soil.

  • tapla
    14 years ago
    last modified: 6 years ago

    Justadncr - not much to add to Stressbaby's reply except that it is rather immaterial what material you use as a wick when you employ it to remove water from containers - it only needs to be mildly absorbent o/a. When employed as an irrigation aid however, it does need sufficient absorbency to raise water to the soil level in the container via capillarity. I have a few plants I grow on an irrigation mat because the containers are so small they cannot go 12 hours without watering. I dangle a small wick on the mat & the plants remain "self-watering" as long as the mat is wet. This is the method that Stressbaby describes, using the wet sand.

    Filix - The number of holes in the bottom of a container is unimportant. One, unclogged hole at the lowest part that collects water is as effective as 20 holes (with drainage as the consideration). Plants don't care if it takes a minute or an hour for soils to reach container capacity (drain). The addition of a single wick would be far more effective than drilling 100 holes in the bottom.
    However, it is very possible, even probable, that plants grown under the eaves would have fungal issues from water continually dripping on foliage or from water hitting soil splashing up on leaves & carrying soil-born pathogens with it. Your friend should guard against this occurring.

    It's good to always remember that air is as important as nutrients and water to plant vitality, so "plain dirt" will inevitably be a poor choice as a container staple due to its want of air-holding ability.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    Thanks Al. Yes I can see now how plain old dirt is a poor choice. I dont know what Would help my freind. Potting in pure perlite or tuface? That would stop the splash and would drain fast. Geraniums from my experince hate wet feet. He has some under his overhang that gets no rain. Sometimes when I check on the place for him those plants are dry as a bone. But are full of blooms very healthy.
    Why is it better to water from the bottom? Or is it?

  • tapla
    14 years ago
    last modified: 6 years ago

    I'm not sure that potting in perlite or even Turface is your answer. It would likely raise issues with required watering intervals and the Turface could get expensive when used in quantity as a soil.

    Wick-watering from the bottom has both advantages and disadvantages. It helps reduce the compaction associated with frequent water flow through the soil, and tends to keep soil more evenly moist than the dry/saturated/dry/saturated cycle we often see when we irrigate heavy soils from the top. On the downside, wick watering tends to concentrate in soils, those solutes that remain after water evaporates. High concentrations of "left behind" metal salt precipitants can eventually make water absorption by the plant material difficult or impossible (plasmolysis). Plants could possibly die of thirst with roots awash in water. For this reason, I would suggest that even wick-watered soils are open enough to allow frequent flushing by a copious irrigating from the top.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    A couple of questions. 1 Im interested in the concept of driling holes at and near the bottom of your wooden containers to encourage for air. I will be making some wooden containers.
    2 Since we know air for roots is very important in containers, how about the ground? Some say not to ammend the ground. Just plant it in the hole you dig and put back the soil that came out of the hole. Because if you add things to the soil eventualy the roots will grow out of the ammended soil and be shocked with the soil around the hole. This is kind of confusing to me. Isn't a raised bed a large container? Why wouldn't the same thing for containers work in the ground?

  • justaguy2
    14 years ago
    last modified: 6 years ago

    1 Im interested in the concept of driling holes at and near the bottom of your wooden containers to encourage for air. I will be making some wooden containers.

    That's what I do, drill holes in the sides of the wooden containers. Something I am considering is adding a PVC pipe with holes drilled in it and covered with landscape fabric. The idea would be to make it easier for oxygen to enter otherwise impenetrable sidewalls. Of course if the wooden container is whiskey barrel like where there are small spaces between wood slats, this goal is already accomplished, but could be further improved, I believe, with an aeration tube. The idea is similar to what some do with compost piles where they want to maintain good aeration throughout, but don't wish to turn the pile often. Some say not to ammend the ground. Just plant it in the hole you dig and put back the soil that came out of the hole

    The only time I have heard this said has been in reference to trees which put out extensive and deep root systems. The expressed fear is that hard clay soil can act like a container if the growing media for the young tree is soft. I don't know how true this actually is, but if you think about it, it is kind of pointless to try and dig out a 10' diameter area 10 feet deep to improve the soil for a tree. Isn't a raised bed a large container?

    Sure is. The difference is that in most cases the 'container' is open on the bottom and in contact with the soil below. This makes drainage less of a concern than it would be in a closed bottom container not in contact with the ground.

    It's that whole 'wicking' and 'perched water table' thing.

  • filix
    14 years ago
    last modified: 6 years ago

    Thanks justa. I like your idea on the pipe. If im going to make wood containers, I my's well make em right. I want to make some that would hold large canna. Like musafolia. Since I have never grown them before, I don't know how deep to make them. I know the rizhomes get put under the soil 2 or 3 Inches. But how deep will the roots get? I was thinking of 20" wide 24" deep. Same for clematis. Just I would do the woody mix thing for the clems, 1. turface 1.bark 1. crushed granite.
    Would you put the perforated pipe in the corners verticle? Maybe it could take up air from the bottom also like a chimney effect. Would you go the full hight of the box?

  • rhizo_1 (North AL) zone 7
    14 years ago
    last modified: 6 years ago

    Shrubs and trees do best in the long run if you don't amend the soil ONLY if you are planting 'hole by hole'. If you are going to prepare an entire bed, raised or otherwise, then by all means...amend to your heart's content.

    The reasons for not amending are simple, once you think about it. Plant roots will tend to grow into an area best suited for them....plenty of air, available water and dissolved minerals, etc. An amended soil is often an 'improved soil', and those roots are quite likely to grow round and round and round within that planting hole, becoming quite literally pot bound within the soil! I've lost count the number of times I've had to point that out as the reason a client has lost a shrub or tree.

    Also, because the texture of the improved hole and the surrounding soil may be very different, the hole may either attract water to it or repel it. Either one bodes severe problems for the root systems of our woody plants.

    Tree roots, by the way, do not put out extensively deep roots. (myth) The most important part of their root system is very close to the surface of the soil, where the highest concentration of oxygen is. The typical root system is very wide spreading, but very shallow.

    By the way, I live in an area with very hard, red clay. The same rules follow for this kind of soil, too. No amending upon planting.

  • justaguy2
    14 years ago
    last modified: 6 years ago

    If im going to make wood containers, I my's well make em right. I want to make some that would hold large canna. Like musafolia. Since I have never grown them before, I don't know how deep to make them. I know the rizhomes get put under the soil 2 or 3 Inches.

    It's somewhat difficult to answer a 'how wide' question regarding container cannas because some will produce more rhizomes than others. There are cases where people placed a single canna in a 10" container and the container cracked from the pressure of the expanding rhizomes.

    I my case I usually cluster 3-4 cannas together in a 22" container. It is 18" deep. The rhizomes are generally filling the width of the container by end of season, but I don't believe I have found them more than 10" or so down. Your mileage may vary. Would you put the perforated pipe in the corners verticle?

    I dunno, I haven't finished 'thinking about it' yet ;-)

    My original thoughts were to place it horizontally, but vertical may have advantages as well.

  • tapla
    14 years ago
    last modified: 6 years ago

    The idea of multiple holes in containers and aeration "devices" is addressed in this thread or the last where water movement in soils was the subject. It seems an ineffectual effort to me. The only soils it could help are those that already have gas exchange occurring and don't need it. Those in which no gas exchange occurs will not benefit because it doesn't improve gaseous movement through soils.

    Think of it this way: If you poke 1,000 holes & insert 25 perforated tubes in a tub of puddin', and do the same to a tub of marbles, which would benefit from the added gaseous exchange? Certainly not the puddin', and the marbles don't need it. The point is that any soil that is structurally able to benefit, already doesn't need it.

    The only benefit of adding more holes and a perforated tube is that it increases evaporative surface area & soils dry down quicker. This decreases watering intervals, allowing us to "flush" stagnant gasses from soils at each watering, if soil structure allows copious watering, (it certainly should, but if it does, the tubes and holes are unnecessary) and allows some additional air to return to soils as they dry down (which would already have been present in any suitable soil).

    I just wanted to note that growing in raised beds in not like growing in containers. It is like growing in the ground, but with better drainage (or soil), and quite different than container growing.

    Al

  • justaguy2
    14 years ago
    last modified: 6 years ago

    Al, the purpose in the aeration tubes, at least according to my thinking, was to increase evaporation in the perched water area.

    I do not prefer light soils as I do not prefer to water every day. I am willing to live with the results of that.

    At the same time, I do value good aeration and the potential for healthier plants.

    I don't see any reason to have a soggy area persist at the bottom of the growing media. If I didn't want the entire height of the medium to be equally useful I would fill it with crushed aluminum cans or some other such material.

    To my thinking the aeration tubes are a means to get better productivity from heavier soils while not significantly decreasing the watering interval. Or at least I hope it ends up working that way ;-)

  • filix
    14 years ago
    last modified: 6 years ago

    I just wanted to note that growing in raised beds in not like growing in containers. It is like growing in the ground, but with better drainage (or soil), and quite different than container growing.

    Would you use same basic soil as containers?

    Since a taller pot is better. More room for roots and lower p.w.t. I should make them accordingly.

    I try to use rain water when ever I can. Catching it with a large plastic drum from the drip edge of my barn through insect screen.

  • justaguy2
    14 years ago
    last modified: 6 years ago

    Would you use same basic soil as containers?

    Not usually. Then again I don't use soil in my raised beds, I use peat, vermiculite and compost ;-) I have used a mostly compost/peat mix in closed containers that I flood with water, but that isn't the norm.

    Raised beds with open bottoms will drain much faster than a closed container with the same growing media. This assumes, of course, that the earth the bed is on isn't water saturated.

    Think of the earth as a great big wick.

    If you use a fast draining container mix in a raised bed you will need a drip system with a timer and backup timer to keep the thing watered often enough. May as well switch to hydroponics at that point. Or start a cacti/succulent bed.

    If you use a heavier mix more suitable for raised beds in a container you will have a drainage/aeration issue.

    Having said that there are those containers growers who grow in pure compost in beds and containers who say they are happy with the results. To each their own, I guess.

  • tapla
    14 years ago
    last modified: 6 years ago

    Justaguy - The tubes will decrease soil volume and increase evaporation; both shorten watering intervals. So now you have a heavier soil than you want (otherwise, you'd have no need to resort to mechanics to increase aeration), a reduced volume of soil, and shorter intervals between irrigation.

    Your "I don't see any reason to have a soggy area persist at the bottom of the growing media." tells me that you feel the tubes are an effective solution to persistent PWTs. Not so. The PWT in any container soil is of consistent height when soils are at container capacity.

    A more open or just a more appropriate soil, and the simple addition of a wick are two more appropriate solutions, neither of which require diminishing soil volume and in most situations, no decrease in irrigation intervals.

    Filix - Because of the constant wicking effect of soils below raised beds, or just because of gravitational aid to lateral water flow, you'll likely want to use a much heavier soil in raised beds than in containers. More often than not, in raised bed growing we're worried about the flip side of the drainage coin, i.e. retaining water.

    Note too, that the PWT height in a tall pot will be the same as in a shallower pot if the same soil is used in both. The advantage is in that: of two containers, equal in volume, the taller will be less likely to be negatively affected by perched water. The reason is because it will have a lower % of saturated soil when soils are at container capacity, and the o/a volume of water in the PWT will be lower, allowing air to return to a higher % of soil, faster.

    Al



    {{gwi:3924}}
    This is an excellent raised bed soil in its 5th year, very rich and with excellent tilth, it would hold too much water and be inappropriate in containers. Note the Turface (tan, irregularly shaped particles), still maintaining shape & functional integrity after extended, repeat exposure to freeze here in zone 5.

  • filix
    14 years ago
    last modified: 6 years ago

    Once again what you said makes sence. For my raised beds how about 1 part peat 1 part compost 1 part turface? The pwt makes sence, as I learned from reading your thread. So I will make my wood containers taller. My friend with his window boxes might be in all the pwt. His potting soil might have a pwt of 4 or 5 inchs. Thats about how deep his soil is. So like you said the wick is the solution. Thanks Al and justaguy.

  • tapla
    14 years ago
    last modified: 6 years ago

    How about?:

    3-5 parts pine bark
    1-2 parts peat
    1-2 parts compost
    1 part turface
    1 part sand

    Al

  • justaguy2
    14 years ago
    last modified: 6 years ago

    For my raised beds how about 1 part peat 1 part compost 1 part turface?

    I can't really say as I haven't played with turface yet. I do like the peat/compost as both are water sponges and the compost provides all the fertility most plants will ever need.

    Perhaps one of the others who have used both vermiculite and turface could give an idea of how each would affect the mix positively and negatively.

    I would say go ask the question on the veggie garden forum or Sq Ft Gardening forum or a forum more appropriate to raised bed growing, but I doubt too many there have used Turface either so here is probably your best bet.

  • filix
    14 years ago
    last modified: 6 years ago

    I want to use screen at the bottom of my wood containers im making. Does insect screen clog up. Is the mesh too fine? I have some white cedar kicking around. Im going to make a couple 19" deep. I dont want ants or any other insects coming in if I can help it.

  • tapla
    14 years ago
    last modified: 6 years ago

    I use insect screening at the bottom of all my containers (except bonsai) with no clogging problems at all.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    Al and others. I cant thankyou enough. This has been like goimg to school for gardening..Filix

  • justadncr
    14 years ago
    last modified: 6 years ago

    Thanks so much. I went to the gardening centers 60 miles away today and was only able to get Orchid bark which they said was a mix of fir and hemlock. It says screened. I couldnt find anything called micro nutrient powder and they didnt have it when I asked. I did get perlite and peat as well as Osmicote. Do I leave out the micro nutrient powder or try to order on line? I dont really have access to a good composted manure. I am starting all this with my houseplants first. Oh I also got some granite particles.
    Also I think I read this months ago also and saw pictures of the different barks but cant find that now. What is the size of bark again? 1/4 to 1/2 inch?
    My husband is a commercial fisherman so I have lots of rope for wicking. Thanks again for all the wonderful information.

  • filix
    14 years ago
    last modified: 6 years ago

    Question. Al do you just put insect screen at the bottom of your wooden containers. OR do you run in up the sides also?...Filix

  • tapla
    14 years ago
    last modified: 6 years ago

    Usually, what I have in wood containers are woody plants that I'm growing on for bonsai. For that reason, the containers are usually shallow & the sides made of a single piece of 1x6 or 1x8, so I only use insect screening on the bottom to keep soil from migrating out the drain holes.

    Al

  • filix
    14 years ago
    last modified: 6 years ago

    Al I was wondering if your recipe for woody plants wood be good for my clematis. I built an extra large wood container 28" x 24" x 24". Your mix is one part screened pine or fur bark, one part turface, and one part crushed granite. I thought maybe it would put off a repot for a few years. Would the crushed granite come frome my local sand/stone company? How fine? bb size? And thanks again..Filix

  • tapla
    14 years ago
    last modified: 6 years ago

    It would be an excellent mix as long as you are willing to commit to the frequent watering/fertilizing that it would require.

    The crushed granite would "most likely" come from a feed store or elevator - somewhere that sells chicken/turkey feed and the grit that they need in their gizzards to grind the food. Ask for "granite turkey grit". Grani-Grit is the brand I use. It is irregular and sharp and it's o/a mass is close to that of a .177 cal. BB.

    Al

  • amyben
    14 years ago
    last modified: 6 years ago

    I see, by what I've been scanning, that it's definitely time for this paper to be returned to the top. Maybe someone could re-post it. I don't know what the protocol here is. Nor, for that matter, do I know how. Do we wait till it reaches 150 follow-ups? I know Al won't do it himself, so will someone help?

  • philoz
    14 years ago
    last modified: 6 years ago

    Hello from a newcomer

    I would like to grow fruit trees and shrubs in containers.
    I am afraid that handling large containers for root pruning and repoting can be a hard job, especially getting a plant out of a container.
    Would it help to have containers with walls that can be easily screwed / unscrewed?
    This question relates to my separately posted msg on the use of fiber cement sheets.
    Thanks
    FM

  • tapla
    14 years ago
    last modified: 6 years ago

    I find that if you're careful about the container you use, that plant removal is usually a breeze. I normally only have difficulty removing plants that are root-bound and growing in terra-cotta or unglazed pottery because hair roots will grow right into wall pores. Flexible & nonporous containers offer non of the minute hidey-holes for roots to grow into, so it's easier to extract the planting.

    To address your cement board question: Cement board could be very surface porous and might present some potential difficulties in that it could raise media pH substantially unless it was well-weathered. There are many manufacturers of different kinds of cement board, some include water tight laminates on one side, so it's impossible to answer your question with any certainty w/o more information.

    Al

  • philoz
    14 years ago
    last modified: 6 years ago

    Thank you AI
    You are right - cement sheets per se can be quite porous and get soaked with water. However they can be easily coated with a water tight paint. It seems that there is no general answer to the question of alkaline toxicity - one has to experiment and measure pH in the course of practical usage.

    By now I have 6-8 month experience of growing in cement sheet raised beds. My pH is around 6.5 with no real difference betwenn the central and peripheral areas of soil.
    Vegetable plants (eggplants, capsicums, cucumbers, melons) are doing quite well.
    Now I am considering building containers for fruit trees - that's the reason to seek your opinion.

    Thanks again
    PM, Australia

  • bjs496
    14 years ago
    last modified: 6 years ago

    Philoz,

    I used Air-Pots last year. I used them only for rooting (which will change this year) but they come in sizes to 120 gallons. One of the nice things about them is they are shipped flat. Therefore, the assembly involves one to wrap the flat sheet and secure it with a "fixing" (in my case its something very similar to what holds the upholstery into your automobile sheet metal.) When it is time to repot/root-prune, you can remove the fixing, and unwrap the container from around your tree in place.

    This is necessary because of the design of the container, but it comes in handy for other reasons as well. The overall design of the container is suppose to prevent (or at least minimize) many root problems associated with container growth. I found it to be moderately successful.

    I posted on the use of the pots in this forum. I think I just titled it "Air-Pots". I seem to remember a distributor in Australia.

    good luck,
    ~james