I think you have it, James. I'm so impressed with how much you've learned in such a short time.

You can grow in a much finer soil when using the method you describe though - I know you already know this, but the earth acts as a giant wick & removes any water that would normally occupy the perched water table in a container.

The roots need more water early on because they are still restricted to obtaining almost all water from inside the container. Since the water will be wicked away by the earth, the plant could easily use all the free water in the container & suffer drought stress, even if the adjacent soil was holding adequate moisture. The air pots do help to substantially minimize the effect, though.

Al

Thanks Al.

This makes perfect sense in a container filled with a growing mix which has at least a moderate PWT. However, it seems to me there would be little difference in the rate of water evacuation between a container above ground and one buried in the ground if they contain a growing mix with little to no PWT. Therefore, all things being equal both containers would require the same amount/frequency of water. Also, at least in Texas where the heat can be quite intense for a long period of time, the buried container will be cooler and will require less frequent watering.

Is this assumption correct?

~james

Yes. The better the drainage/the larger the particulate size - the smaller the effect of anything like pot-in-pot, pot-in-trench, or simply burying the container will have on water retention until particulate size of the soil approaches 1/8 inch & the effect is near 0. At that point, the benefits of burying the container would lie primarily in the temperature buffering affect & the plants access to naturally occurring soil nutrients.

Al

James,
1. Aside from watering, the root systems as they grow to the edge of the pots will be exposed to far less damaging heat from the direct sun on the pot which will increase the root mass at a much quicker rate during the summer months. Even in Hawaii we coated the outside pots in rows to lessen the root damage from the high heat gain of black plastic with a 50/50 water and cheapest white latex paint we could get. Depending on how bad a given winter is your freeze damage to roots will also be quite a bit less again adding to the overall growth and health of your in ground trees.

Question: With your heavy gumbo clay soils in Houston and the relatively high rainfall is oversaturation possible? The variance in particle size between the heavy clay and the airpot may cause migration of excessive rainfall back into the air spaces in the air pot from the surrounding soil if the water tends to pool and puddle for extended periods. I believe that many tree farms use mounds or gradually slope areas to keep these issues at bay.

BTW I wish I had enough soil here to do in ground! I do feel that in most cases this is the way to go and more and more tree farms are seeing the benefits out weigh the intial costs in the long run with this growing technique.

What kind of trees are you growing? I am getting a few hundred mexican white oak started this year. The oak wilt problem looks to get a lot worse before it gets better and MWO seems to be a good one to use for replacing the lost ones and to lessen the risk for all areas with problems already.
Good Luck and happy planting. David

Hi David,

I grow mostly figs (114 trees/58 varieties) and pomegranates (16 trees/10 varieties and growing) for my own enjoyment. I don't have space to plant in the ground in Houston. However, I have some I am planning to plant north of Austin. Part of my brother's property is an old horse pasture. The soil looks dark and rich (I haven't dug into it). I have planted a few trees into the ground in the yard where the soil is dry and hard. I am told the soil is fairly shallow and underneath is limestone. The motivation to bury them here is to take advantage of growing conditions I don't have in Houston, while still maintaining some semblance of portability.

I wouldn't plant them in Houston. The reason I grow in containers is an RKN infestation in my yard (actually they're everywhere in Houston). Tress planted directly into the ground seem to do pretty well in Houston, despite the soil, moisture and nematodes.

~james