From another post: How large a container needs to be, or CAN be, and how much soil a planting needs/will tolerate before drainage & saturation is an issue depends on the 3-way relationship between plant mass, container size, and soil type. We often concern ourselves with "over-potting" (using a container that is too large), but "over-potting" is a term that arises from a lack of basic knowledge about the 3-way relationship noted, which should logically determine appropriate container size(s).
It's often parroted that you should only move up one size in containers when "potting-up". The reasoning is the soil will remain wet too long and cause root rot issues, but it is the size/mass of the material and soil type/composition that determines both the upper & lower limits of appropriate container size - not consecutive volume progression.
Plants grown in slow soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil. This (smaller soil volumes) and the root constriction that accompanies it will cause plants to extend and gain o/a mass much more slowly - a bane if rapid growth is the goal - a boon if growth restriction and a compact plant are what you have you sights set on.

Conversely, rampant growth can be had by growing in very large containers and in very fast soils where frequent watering and fertilizing is required - so it's not that plants rebel at being potted into very large containers or volumes of soil per se, but rather, they rebel at being potted into very large containers with a large volume of soil that is too slow and water-retentive.

We know that there is an inverse relationship between soil particle size and the height of the PWT in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (saturated).

So, if you aim for a soil composed primarily of particles >1/16", there is no upper limit to container size. The lower size limit will be determined by the soil volume's ability to furnish water enough to sustain the plant between irrigations."

You can grow a very small plant in a very large container if the soil holds little or no perched water (saturated soil).

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Because you are looking for a crop, you should also consider the effects of growing in a container with the plant under root-bound conditions. This slows branch extension and decreases leaf size, which effectively reduces the amount of food (photosynthate) the tree can make. This means the tree will have less energy to put into producing fruit. So, it is best for fruiting to grow in a large container with a fast soil so roots have plenty of room to stretch out and to pay attention to pruning roots on a regular basis.

Al

Thank's for the information, it will be quite useful.

Unless you have a paved flat area and the pots are on rollers, you won't want to go over about 30 gallons. Use a potting mix high in Pumice and try to avoid heavy sand. Sand won't hold moisture anyhow. You will have to 're-pot' every few years, or the roots will circle around and choke the main tree. It is a lot more work than planting in the ground. Violet De Bordeaux is a good smaller tree to try in containers. Mike McConkey at Edible landscape can probably suggest other good varieties for containers.

Here is a link that might be useful: Edible landscape

I have come into some 55gal food safe drums, how much should the be cut down for optimum use?

I'm growing all kinds of fruits very successfully in pots no bigger than 15 gallons. Friend came up with some superior 30 gal pots for free. After using two, I don't want any more. They are just too heavy.

Many of my stone fruit trees, citrus, and figs have been in the same pot for 5 to 7 years without repotting. The vigor and health of the trees are great. Fruit yield and quality outstanding.

Rob, just do what Ray Givan does - cut that drum in half, and now you got two big pots ;)

Hi, I wonder if I can use big container to simulate in ground planting. Say use a 35 gallon (24"D x 19" H) for a 2-year old young fig tree. Grow for 5-7 years without re-pot. Would normal garden soil + potting mix + compost work well for this? Given the mix won't be too wet and there are enough drainage holes poked, planter will be 4-6" put into ground with possible roots going out of drainage holes too.

Thanks,
-Layne

The reasons of doing that are 1) would consider getting a larger house/lot within 5 years, better chance reporting the trees then if growing in pot. 2) Neighbors might respond better to growing stuff in container than digging up the lawn consider it's a town house community.

From the perspective of soil hydrology, partially burying your containers turns them into raised beds, and you can get away with things that would be very counter-productive in conventional container culture, but you still need to be somewhat wary of soil compaction. You might wish to use a mix of ingredients large enough that compaction will be less of an issue, because the organic fraction of the soil will pretty much have disappeared over a 5 year period. I think a 50/50 mix of fine pine bark and Turface, with a little vermiculite and maybe some very coarse sand (half BB size) would give you excellent results over the long haul for the application you described.

Al

Ditto to what Lou and Al said. I also use the big 20 gallon tubs for about 5 of my trees. Just make plenty of drainage hole and root prune your tree every 3 years and they will be fine. Get a good hand truck and strong bundgee cords to help you move the trees around your yard. The tubs I use have those white rope handles but for safety reasons, I don't recommend using those. THey will break if the tree is too heavy. Plus the hand truck will save your back! cheers, Dennis

I cut the 55 gal drums in half with a jig saw, gave me two 27.5 gal drums that hold about 25 gal of my soil mixture. Makes thing easier when doing calculations. I put about 16 1/2-3/4 in. holes in the bottom of each with a step drill, best tool for this. I also put some holes for rope handles. They are not unmanageable and drain well. It's been about 3 weeks since I transplanted after I severely pruned back the roots (pretty sure I took too much off) but they are beginning to leaf out finally, may even get some fruits.

Rob I love the pots you made. The only thing I would do differently is the holes. No holes in the bottom only on the sides. With holes in the bottom you run the risk of the trees rooting through the bottom of the pot which can make the tree hard to move.

Like Layne I plan on putting them in the ground about 6" deep. I plan on marking the pots where the side holes are to make it easy to cut the roots when its time to move them.

Old post, I know, but it should be said that, if holes are to be made through the sidewall, at least one of them should be tangent to the bottom of the pot. IOW, the bottom of at least 1 hole should be exactly even with or slightly below the pot's bottom. "Slightly below" would entail removing all, or a portion of the upper surface of the bottom in the immediate vicinity of the hole in the side. The reason for this would be to avoid the pool of stagnant water that will accumulate in the bottom of the pot whenever holes are drilled through the side and above the pot's bottom. Even 1/8" of water at the pot's bottom is too much, this, because it will increase the severity of the issues associated with perched water in the pot.

Al

Hi Al,

Lazarus thread...I did get roots growing through the bottom holes but really not to bad to move at the end of the year. What I do now is put a sheet of heavy black plastic under each pot, water still drains out, problem solved.

Rob

I disagree with @tapla. I have been growing figs in pots for four years. I have about 80 fig trees, all healthy and growing vigorously.

I (and some fig experts on the Ourfigs.com forum) put eight 1 inch holes around the bottom as close to the bottom as possible and I have not encountered problems, probably because figs are water hogs.

I do not think it would hurt to put holes in the bottom but that would encourage roots to exit the pot and go into ground.

I am in zone 5b, central Massachusetts. Things may be different in an environment that gets more rain than I do.

V said: "I (and some fig experts on the Ourfigs.com forum) put eight 1 inch holes around the bottom as close to the bottom as possible and I have not encountered problems ...."

Why as close to the bottom as possible? Because drilling them above the bottom is a problem. And as far as drainage is concerned, 1 hole is as good as 8 or 100. I assume the experts are expecting the extra holes to facilitate gas exchange, which also serves to compound the issue of the soil drying down too fast. Either way it's hard to justify the holes by way of efficacy.

Whenever the oxygen supply to roots is limited, even for periods of time as short as a few hours, there is a resultant loss of potential in terms of growth and vitality. It is as undeniable as the conclusion that breathing through a drinking straw while attempting to run a marathon will limit a runner's ability to perform; and, arrival at the conclusion no damage is done because the damage is not conspicuous is a logical error - a causal fallacy in reverse. The damage isn't conspicuous, therefore it must not exist.

We know with 100% certainty that perched water in a container is indeed a limiting factor. Drilling holes through the sidewall, above the bottom of the pot, adds to the volume of excess water in the pot after a thorough watering. How can it NOT be limiting? That the excess water is used rather quickly only suggests that the extent of the damage is limited but not eliminated by the short duration of soil saturation.

If you carefully read what I said, you'll see I affirmed that holes drilled only through the side of the pot (with none in the bottom) should be avoided unless the bottom of the holes are tangent to (touching) the bottom of the pot. Even if the bottom of the holes through the pot's sidewall are 1/8" above the bottom, the pool of stagnant water which has no path by which to exit the pot is a perfect place for anaerobic fungi to gain a hold and wreak havoc with root health/ function. There is a reason you have never seen a container available for sale that has holes only in the sidewalls well above the pot bottom. Like orchid pots, they all have holes in the bottom. Even nursery cans in which holes are punched through the sides have a small portion of the bottom removed directly under the holes ..... for a reason.

Al

Al, thank you for your response. What you say makes a lot of sense.

My tree containers rest directly on the ground. At least in my case, the reason for putting holes in the wall, instead of the bottom, is to prevent roots from exiting through the bottom hole and into the soil, which would make it more difficult to remove the pots when bringing them indoors for the winter.

.... and what you said makes good sense as well. If I can take a moment to muse, I almost always approach issues from the perspective of what's best for the plant, but we very often choose to make compromises because of how our individual priorities are ordered, or are forced to make compromises due to the hand Mother Nature deals us. I think it's important to avoid criticizing other growers for their compromises, but perfectly appropriate to point to their limiting nature when they're being made.

There is one thing to be aware of when depending solely on holes through a pot's sidewall when there are no holes in the bottom. In most cases, pots that have a hole in the bottom and are resting on the soil are best fitted with a wick, a piece of cloth that bulges through the drain hole, or no barrier at all at the drain hole; this, so there is continuity of the soil column from the top of the soil in the pot all the way to the earth below the pot, an essential part of putting the earth to work as a giant wick to help drain perched water from the grow medium. If the soil column is broken at the bottom of the pot, wicking action ceases and water perches above the pot bottom, no matter the location of the hole(s). Any of the 3 fixes I mentioned will work whether a drain hole is through the bottom or through the sidewall AT the bottom.

Al