Anybody tried raised beds for fruit trees?

When we went to plant these fruit trees and started digging, we realized that there was less than 4 in of topsoil before hitting the Limestone that's called caliche here in Texas. So I decided to bring in 5-10 wheelbarrows of good clay loam and build up about 6 to 10 in of soil in which to plant trees. Has anybody else tried this method, and how has your success been? I realize that over time the tree's roots are going to want to spread further so we'll need to bring in more topsoil and move the rock walls out further. I also realize that the raised beds will require watering, basically forever, unless I extend them out basically forever....

Speaking of Tolstoy, there is a misconception that Caliche is impermeable. AAMOF, our local Water Conservation District says that 80% of local stock ponds fail because of ... Caliche bottoms, full of small cracks.

I bet it'll work, and that if you water deeply and mulch/use compost tea it will help even more. I've planted trees in raised beds in areas with a high water table. I know of a woman who grows peach trees in swamps like that. Since the limestone is permeable like you say, I bet the roots will reach down in search of nutrients and water--especially if you water deeply, which will send both moisture and nutrients further down.

If your topsoil is that thin then it looks like you've latched on to the best possible solution for your circumstances. Watch out for wind, especially as the trees get more top growth, as they may not be rooted very deeply in the ground and it will take less force to throw them. I'd probably prune them hard to keep them small and reduce that risk.

I have had problems with my citrus because of heavy clay soil which is wetter than citrus likes. Since they will grow in my area with shelter from freezing weather. I tried 12 inches of garden soil in a 4 foot fiber glass ring. Then surrounded the trees with wood chips outside the 4 foot, leaving the garden soil only around the trees because the roots like well drained soil.and it is in my food forest. I planted comfrey by each tree. They are taking off where others did very poorly and eventually died. This is my second year since planted. They suffered from a late frost but are still thriving. Will keep progress posted. I am in Central,  Louisiana and it is zone 8 to 9. I also removed the rings after I filled them with soil,  planted the trees and they were established for a few months.

Any kind of raised bed dries out too quickly here, so I have basically given up on trying them.  Another drawback to planting trees in raised beds is that they may be subject to being blown over in heavy winds.  On our land, grass grows in the deep soil areas and trees grow in the shallow soil on top of rock. We have lost some native trees to toppling over in high winds due to these shallow root systems.  Smaller trees seem to have less problem with toppling, as they are protected by the taller trees (except they may get crushed if a big tree gets blown over on them).

I'm hearing advice to 1) watch out for wind and 2) keep them watered.  Thank you for that.

Our soil here is called Bolar Clay Loam and it is heavy. It loosens up when wet and can even flow a bit with our heavy TX rains. So I walled it up there with cedar branches and rocks. But when it's not soaked, it is excellent for wind resistance. I think I'll address the wind risk by making those trainer stakes permanent. We already have to sharpen the bottoms with a cutting disk before driving them in, and I welded up a 30lb driver from heavy pipe. When we hit the Caliche hardpan and we can see soil bouncing around us for several feet, we usually stop. The next good long rainy week we get I will drive them down right into the Caliche and use heavier wire, with an eye towards leaving the trainers in for several years.  

There is another school of thought, however, that trainers actually reduce a young tree's wind resistance, and as such they should be removed after one year or so.  I better research that. We're in zone 8 and like most of Central TX we get occasional heavy straight line winds. We don't get tornadoes to speak of, exceedingly rare here in the Hill Country.

In my county (Kendall) we average one tornado a year. Considered a moderate tornado risk area. Back in the 70s I got to experience being in the path of one which blew down our old barn, tore the porch off the house, knocked my grandmother's mobile home off its footings, and of course knocked over a lot of trees, mostly large oaks.  

I really like your rock and log border!

I would recommend leaf mulch also. It will create leaf mold as it breaks down which can significantly increase the moisture retention of the soil.

I like to use shredded leaves as a bottom layer, which will break down quicker and create leaf mold faster, and then put whole leaves on top of that which will break down slower and be a long lasting mulch and weed barrier!

I wander if there was a way to dig down to the limestone and break it up just a little so the roots could get down in the cracks and anchor a little, and further break up the limestone so the water and soil could seep down too!

The mulch on top should also further increase your topsoil as it breaks down.

Looks great!

I grow nearly all of my fruit trees in raised beds (to elevate the rootball above the water level in a spot that floods twice annually), but most aren't far enough along where I can tell you if it was a bad idea. I have about 20 beds like that (half my trees), so I hope it works. =D
They are about 3 years old and doing great, but haven't grown so large yet that I know for sure whether the boxes are a problem.

I made my beds out of 2x10" pressure treated lumber (2.5 x 2.5 feet square), and I dug below the bed so as to not make a hard division between the normal soil and the supplemented soil. I also mixed the normal local soil (a tad too clay-ish for my liking) with the supplemented soil in the box, so the tree gets used to the natural soil. It's about 80% soil from the area.
And I bury fish corpses, cow manure, vegetables, egg shells, turkey intestines, chicken entrails and corpses, chicken bones, etc... whatever I can get my hands on to gradually break down underneath the trees. I usually put it down a decent ways, so it'll break down quite a bit before the tree roots reach it.

After three years, the trees haven't been in any way hindered by the raised beds, but I figure if they ever are, I'll just come along and unscrew the boards, or - worst case - use a chainsaw to cut the boards off. I suspect the tree roots will just burst the beds on their own if I did nothing - I mean, tree roots crack through concrete...
But taking the boards off is basically my plan irregardless of if they need it or not. Being more into hugelkulture now, I intend to eventually cut the boards off, stack tree logs around the beds and form a hugelkultural mound in place of the raised box, and grow something on the mound to help it not get eroded.

My newer trees (5 of them) are just using logs as a plantbox to raise up the soil hoping the logs will eventually break down and provide a hugelkultural benefit.
(I fix the logs in-place with weedblock fabric and chicken wire, with bricks holding it all down so the water doesn't wash the logs away - again, flood zone)

To my (ignorant inexperienced eyes) nothing about your mound looks bad, assuming you're going to mulch it like crazy to improve soil and keep weeds down.

Are all the various forum names explained in a glossary? Thanks.