ashley:

Maybe I could offer my opinion while you wait for Carla. I've been growing stone fruit and blueberries in containers about 5 years. This year I'm using a mix of about 50% pine bark and 50% coarse compost. My mix last year was too dense. None of the trees died, just didn't do so well. I have trees that have been in the same pot at least 4 yrs without repotting or root pruning. I repotted one tree this year. It wasn't easy. I think I'll just start new trees every 4-5 yrs instead.

I've used both semi-dwarf and standard stone fruit rootstocks. Both work, standard maybe a little bigger but not much pruning needed. The small soil volume dwarfs all that you'll need. This is also the opinion of Tom Woods who does this commercially in Centralia WA. I think he calls his operation All Season Fruit Company.

My pots are black polypropylene nursery pots. I've had no problems with root overheating outside or in my greenhouse.

Fruit size is smaller in pots and quality maybe more variable. But some of my best stone fruit most years comes from pots. I'm planning to go more that way vs in-ground.

Fruitnut

So glad you chimed in.

I'm growing some mango trees in containers. How big are your containers compared to tree size?

Here is a link to what I believe is the most popular thread on the entire Gardenweb site. As of now, it's had over 1300 responses and spans 10 separate threads. It takes a while to read through, but is a must read for your container growing medium question.

Here is a link that might be useful: Container Soils - Water Movement & Retention

Wow--a question just for me!

Ashley, you make me sound so organized! If only I had a "system" I use. Mostly I have plans that get lost as time flies. This "employment" thing keeps interfering with my gardening time!

Except for my mulberry, all my trees (75? 80? who's counting?) are in pots because someday the housing market is going to improve and I can sell my city house and buy my little country house-with-acreage and plant them in the ground, but until then, I call them my "pet trees".

For several years I have been using the fake-clay plastic pots from Walmart, because they the only ones I have found that are thick plastic with no rims (plastic rims break off and crack after a year or two), and they were $10 for 22 to 24 inch diameter pots. They recently added self-waterers to these style of pots, and jacked up the price to $22. You can still find the old ones at some Big Lots, now "reduced" to $12.

Last year I intended to switch the oldest pots to lug-tubs with handles--easier to move, much more growing room. I was going to do it during the dormant season, but unfortunately my early peaches and apricots started blooming a week ago, so once again, I'm late with the schedule. I may have time and funds to buy a bunch of lug tubs and soil in a couple of weeks, so I will try then, weather permitting. I am looking into using a hoist or an engine lift to do the pot transfers, because the hardest thing on the plants (and me!) is getting them out of their pots. The plan is to wrap a soft rope around the trunk and hook up to the lift, hoist them 3 feet out of their pots, slide the new pot underneath, then lower into new pot and new soil. We'll see how it goes.

The medium I use is 1/3 to 1/2 my garden soil, and the rest organic potting mix, or for multiple pots, I get a yard of quality soil delivered from the gardening center. I have tried to grow vegetables in straight potting mix, and they are always happier in soil, so I think the mixes must be missing a certain something. I can't use straight soil because I have adobe clay for soil, and the pot would be far too heavy for me to lift, and for the plant to grow, too. As it is, I have to strap them onto a dolly to move them around. I have seen an dolly actually designed for moving pots, but they are over $100 and it's on my wish list.

Hope this helps!

Carla in Sac

Brandon 7, thank you for providing the link. Amazingly lucid and comprehensive writing for a thread. Definately something I'll keep in my e-brary.

I'm growing one to five stone fruit trees in 15 gallon pots. That's five trees on standard size, Lovell, root stock; or more commonly Citation semidwarf; in one pot. They bloom and fruit the second year. So much for three trees in a hole, this is really high density, and it works.

Thanks all for the responses. Fruitnut and Carla, I am encouraged by your successes with potted fruit trees. I am happy to have an excuse to buy all the trees that I like instead of being choosy. And I never thought of the concept of multiple trees in one pot! You set me off on a new path now! And here I was worrying about how my in-ground multiple trees in one hole experiment would do.
BTW/ could both of you also share what your fertilizing regimen for the trees in containers is? I am assuming that it is more often than the in-ground trees.
Tammy, I have an ice cream mango in a pot now, thanks to your blog.
brandon, thanks for bringing up Al's very informative thread. I see so many success stories in the citrus forum on growing container citrus using the Al's soilless mix.

I apply about a teaspoon of ammonium sulfate about once a month in each pot. Probably 3-4 times a yr with a complete fertilizer. This is usually the stuff you put on blueberries.

Here are Al's thoughts on a fertilizing program for containerized plants. I noticed the link, in his other thread, to this thread doesn't work.

Here is a link that might be useful: Fertilizer Program for Containerized Plants

As with sautesmom I have been growing in ever larger pots awaiting my acre-and-a-half in the country. I use commercial pots for their strength, sensible deign, and long life (UV protected). They are too expensive in the retail trade. I buy them up to 17 gallon size (if available) very reasonably from commercial landscapers (the standard "used" price last time was 5-8 cents per gallon) but 25 gallon sizes are hard to find and 45s about impossible (the landscapers reuse them themselves). I buy the larger ones wholesale (and thus a reasonable price) from a big nursery supply outfit about 80 miles, preferably when I'm nearby for other reasons. I have to buy at least 20 10s or 10 25s or 5 45s, as that is how they are bundled.

I use half or more finer pine bark in the medium too ("soil conditioner" in the bagged retail trade), usually with just some peat moss to fill the spaces between the bark particles (proportion needed varies batch to batch), plus a little limestone and cottonseed meal or soya meal (pretty cheap in big bags used for animal deed).

The secret to reasonable priced gardening is getting AWAY from the retail trade for supplies (except when you can buy "big" such as the standard 40 lb bag of basic 10-10-10 or 13-13-13 fertilizer and the "soil conditioner," which starts as a waste product, has no gardening "magic" to its name (manure, compost) and thus remains not outrageous in price. The soya and cottonseed meals fit in this scheme a bit differently. There you don't buy small, the little bags at the big box store. You find a good feed and seed store and buy the big bags used mainly for feeding horses or other livestock. Same with perlite and vermiculite, buy the big bags wherever they are sold. Look for people in blue jeans and flannel going in and pickups outside, not designer jeans and BMWs (though with the "horsie" crowd you may see a few of them mixed in at the good places).

The hard part of this big container growing for replanting, and which I am now dealing with a bit, is shaking that potting soil off in order to plant "bare root," as otherwise I fear I will be faced with a trunk-base hole because the organic potting soil would eventually rot away in future years.

(BTW, while I don't have time to go through it now, the posts I have seen in the past on the "hydraulics" of drainage in pots, especially pots with coarser material near the bottom, do not stand up in rigorous examination. It is not so much that they are wrong but perhaps a bit overwrought and with definitional uncertainties. Moderate delays in drainage at a soil textural boundary [as a pressure wave passes downward] do not necessarily spell any horticultural trouble at all. A few hours delay is no problem; a few days or weeks [as in true "perching" of water tables] would be a problem. The former seems much more likely in a pot with decent soil.)

goneb: I to have thought that as the organic potting soil decomposes, the soil might sink. Mine hasn't in 4-5 yrs. I think the roots become thick enough to support the plant.

I haven't repotted because the vigor has remained high. A citrus potted in California in 2002 grew three ft last yr. Why repot that? My blueberries potted in 2004 are still getting bigger and setting way too much fruit. Why repot those?

A lot of what Al says sounds good in theory but might not apply to fruit trees.

"A lot of what Al says sounds good in theory but might not apply to fruit trees."

Can you be specific? I haven't examined Al's post thoroughly because I understand the gist of what he talks about anyway, so I may have missed something. But, from what I saw, everything he said can be applied to most anything grown in containers. The physics of drainage and aeration don't change with what's grown in the pot, although needs can vary.

Also, Al's science is solid. There is nothing like "pressure waves" even mentioned in his posts. Anyone that understands drainage would know better than that. I'd recommend anyone, not thoroughly familiar with the science behind soil drainage, use Al's document as a starting place for their research needed to successfully grow plants in containers for longer periods of time.

I was mainly referring to the fertilizer post from Al. All the talk about how applied fertilizer should be in the same ratio as ave plant tissue. If you grow in soil free mix maybe so. That is basically hydroponics. But much of that is aimed at those growing foliage plants, not fruit trees. Many citrus growers on the citrus forum are basically growing a foliage plant. They want the tree to grow all the time because that is the "look" they want. My trees are grown for fruit eating quality, not foliage. Too much water and nitrogen can ruin fruit quality, of that I'm sure.

Also on the subject of drainage, if you read all that you think an organic/soil based mix will never work. But I've never lost a potted tree. Many are 4-5 yrs in organic/soil mix and thriving. Some 7-8 yrs. They grow and fruit fine. If they didn't they'd be gone in a week.

So I appreciate Al's knowledge on the subject. I've gone to better draining mixes on his advice but not soilless mixes.

Fruitnut, I'm pretty much with you. Al's advice is very well articulated but nothing is as absolute as a good article would make seem. If you allowed for all the variables people would get very confused and loose confidence in your advice.

One question I have to ask is, if a perched water table creates such inhospitable conditions at the base of a pot, why are my potted trees always well rooted right down to the base of the pot (excepting GDMD pears)?

I've been aware of this issue since I was in hort-school reading Carl Whitcombs book. Researchers always speak in absolutes, practitioners often find a lot of exceptions. I've started using wider, shallower pots in my nursery so I don't have to remove so much root from the plants I pull from the ground. So far, after one complete growing season, the trees haven't suffered from what should be a much increased PWT. In fact they seem to have benefited from the additional roots.

"One question I have to ask is, if a perched water table creates such inhospitable conditions at the base of a pot, why are my potted trees always well rooted right down to the base of the pot (excepting GDMD pears)?"

What ever gave you the idea that a PWT was necessarily a bad thing? It's not, and is actually an important condition for successful container gardening! That's one reason we don't use large gravels, orchid chunks, or some other very course material for a potting medium. Understanding the principals behind PWTs (as part of understanding drainage in general) is important. Al never said that a PWT was a bad thing (at least not that I've ever seen). He introduced the term to explain how drainage works and to lead into important considerations in choosing particle size.

PWT can lead to bad conditions. Take, for instance, a large pot filled with clay. Anyone familiar with this will know that, for most instances, this is a recipe for disaster. However, if proper moisture levels are maintained, such a container medium can work just fine. Understanding concepts behind the PWT explains why such a medium is not practical for normal conditions.

"There is nothing like "pressure waves" even mentioned in his posts. Anyone that understands drainage would know better than that."

Anyone who really understands soil drainage (i.e., vadose- or unsaturated-zone hydraulics with respect to percolation or infiltration) knows exactly what a pressure wave is. One has to know what it is to understand. This is not the time and place to go into it though.

But without going into the downward-movement aspect, one thing that coarser material at the bottom would certainly do is shunt the draining water laterally to the drainage holes more readily. It would also allow better gas (air) exchange into the lowermost soil. That said, for the most part with decent potting soil (not too fine or dense) it is totally unnecessary.

GB, I didn't bother to quote your entire paragraph, but I think my point was still pretty clear. Al didn't introduce the term "pressure wave" at all in his article (that I saw), and his writing wasn't "overwrought", overthought (if that is what you meant to say), or full of "definitional uncertainties." I think his post would "stand up (to reasonable) examination."

Maybe I'm taking you wrong, but it seems you want to dismiss Al's article without providing justification. I'm sure there is some detail not worded optimally, but overall it's a darn good attempt, especially for a Gardenweb post. If you think you can do better, PLEASE DO!! I'm sure we could all use a refresher. Otherwise, I see no need to criticize it, especially before you have "time to go through it." A vast number of people seem pretty impressed with it from what I've seen.

A number of studies show that adding courser material to the bottom of pots is counterproductive. The larger pore space is quickly filled with smaller particles. The usefulness of such a technique is an old-school myth, majorly busted.

Here is a link that might be useful: The Myth of Drainage Material in Container Plantings

Brandon 7, I am not attacking here. I am not an expert on the dynamics of pot culture although I've grown thousands of trees in pots in my nursery with mixes I've made. I can't control moisture levels because these pots are outside and I'm in the northeast.

I was steered to using relatively tall pots based on how I understood Carl Whitcomb's explanation and advice and I believe even Dave suggested that taller, narrower works better than wider shallower pots as far as useful space for the root system relative to total area. If the roots seem to colonize the perched water area with the same density as the rest of the pot in very wet seasons and dry it raises some questions for me that you are not answering.

All the experiments I've seen only show the slow drainage of water above the PWT, but don't explore what happens to the roots there in the long term. Not saying such experiements don't exist, just haven't seen them.

On another subject, I always thought the main reason for gravel on the base of a pot these days was to keep the potting mix from falling out of the pot.

I try to write pretty precisely. I wrote "the posts I have seen in the past on the 'hydraulics' of drainage in pots" intentionally, to get away from the specific article you referenced as I didn't have time or inclination to go through it right then. The posts I refer to were related in topic and on Gardenweb but in another forum (I forget which). They invoked a zone of saturation perched in the finer soil just above the bottom coarser material. That made no sense to me hydrologically. I (back then) briefly looked at what professional soils hydrology (soils physics) literature had to say about it and saw that it was not in fact any true perching of saturation, especially not likely long enough to do any harm to roots, but was merely a delay in the downward passage of the pressure wave (relates to percentage of saturation). And if I recall correctly (it's been a while), the only time you got saturation at all above the textural boundary is when the finer soil is very fine and is capable of holding saturation there by capillary tension. Clays or fine silts are not what we want as potting soil in any event.

The possible definitional problem I referred to was the probability of horticulturists defining perching or an elevated zone of saturation differently than a soils physicists would, even if both were agronomists. A ground water hydrologist would look at it still differently. A soils physicist would tend to look at perching as saturation in a steady state (stable except for evapotranspiration); a horticulturist or orchardist or farmer would look at it as perched if it stayed there long enough to do some harm (or good); a ground water hydrologist would not pay much attention to it unless it lasted for months or years (except possibly in terms of inducing lateral flow in recharge events).

Here, I again refer to those earlier posts: I think the notion that coarser material at the bottom of a pot is in any way harmful in terms of drainage IS a horticultural myth. The point may be well taken that the older notion of its necessity may be a myth too.

Well, since this is my own, personal post [:)] I want to try and steer it away from hydraulics and oversaturation (maybe start a new posting for this???) and back to the original question.
Since Ashley and I are both in California, we are MUCH less concerned with pots not draining and much more concerned with adequate water and the trees not suffering from water stress in the 9 months without rain. And I will also say, I don't worry about fertilization much, except for the citrus, which will turn yellowish if I don't feed them/give them iron at least twice a year. I get yummy fruit from all my trees even if I don't give them anything, and just repot them every couple of years with new soil.

Carla in Sac

Carla,
Drainage is, by far, the prime factor one usually considers when choosing a medium. If you discount drainage, the type of medium one uses is of much less importance. Even durability issues are mainly related to future drainage issues. Also, the availability of water, you just mentioned, is determined partly by drainage. Choosing a potting medium without considering drainage is like buying a house without checking inside.

Except that drainage is not such an issue if you live where it does not rain during the growing season. Soil is always a superior medium to artificial soils (cubic inch for cubic inch) if you can assure adequate oxygen.

Carla seems to be doing very well with a high soil content mix, which in the west doesn't surprise me. You can grow as much tree in 20 gallons of soil as 50 of artificial mix (made up the math but you get my point).

"Except that drainage is not such an issue if you live where it does not rain during the growing season (and you are using plastic plants)" However, live plants need irrigation and good drainage.

"Soil is always a superior medium to artificial (potting medium)...if you can assure adequate oxygen." Of course, potting medium is usually used instead of most soil because this is generally not practical (depending on what soil is being used, of course). And, drainage is what provides adequate gas exchange in soils. Without drainage you have only surface gas exchange.

Some natural soils may work fine as a component in a potting mix. Analyzing and understanding drainage, or doing lots of trial and error testing, would be necessary in determining which soils would work and what amounts should be used. I guess it boils down to...you either understand drainage, take the advise of someone that does, or count on blind luck.

And you are Felix to my Oscar.

If you can control the amount of water during the growing season and than let the soil stay excessively wet during winter and leach out surplus salt, soil apparently can be an affective medium.

I was surprised when I recieved my first trees from Forest Farm in Oregon years ago. They were using a pure soil medium in their small pots and producing many thousands of trees efficiently this way. I don't know how they did (do?) it.

When Carla says she makes a mix with half garden soil and it works well for her and has for years, I have to believe that she is running with what works best for her in her arid neck of the woods. Good enough for me.