I can't begin to help you with the soil question but I would have thought figs would be happy in those conditions with no fancy treatment.

Scott,

As long as it's not solid bedrock you should be able to plant your trees without any berms. The hardest part could be the actual digging. It sounds like you may need a pickaxe.

Trees will establish in the most rocky soils as long as moisture is adequate. The limiting factor may be nitrogen, so it might be a good idea to add some fertilizer until the trees are established.

Should have mentioned, don't add any fertilizer in the planting hole. Just top dress.

I lved in San Antonio with the same soil conditions. In my view, you have two choices, 1) Use a pick ax or jack hammer to break up the caliche and improve the soil by adding appropriate soil and compost, or 2) Dig as deep as possible and put in good soil in the hole and build a raised bed above it. I planted persimmon trees in SA using the first method and it worked fine.

I see Charlie beat me to it but I recommend renting a jackhammer, both with the "spade" (wide blade) tip and the pick tip as you will need both. This is probably a project where you have to bring in some buddies, the jack hammer is hard work and you may need to alternate, while someone else shovels the debris out of the hole.

Suggest you speak with your County's Master Gardeners to ask about how to best manage your soil.

Look here
http://aggie-horticulture.tamu.edu/travis/GotQuestions.htm

Here is a link that might be useful: Travis County Master Gardeners

Scott:

If there are big trees around I'd not dig any deep holes in the rock. Big trees, if not irrigated heavily, indicate they are rooting through the rocks by themselves. In my view building a bed would be easier.

With the right rootstocks and proper irrigation the trees will probably do alright planted just in what you have. I'd go with MM111 for apples and things like Lovell for stone fruit. Them mulch around the trees and control weeds.

My buddy has soil just like you describe. Trees will grow there with proper irrigation. I bought a place with soil like that in 2003 and will admit that I soon sold it and bought my current place.

Thanks for all the replies. My previous house has similar soil and I dug as deep as possible before reaching the solid rocks (around 12" deep). Water does not drain out easily from the holes though. It can sit there for a few days...

So I will build up but not down this time. I do have some 20-30 feet tall oak and cedar trees in the yard. I am sure somehow they manage to grow without irrigation.

Regarding raised beds, what soil should I use? Should I dig the sub-soil to mix with the foreign soil?

Scott:

I'd use the best soil you can find. Around here they haul in bottom-land loam or clay loam to make raised beds. And it doesn't need to be mixed with the native soil. What you bring in will probably be lower pH than the caliche so I'd keep the best soil on top.

How do you plan to water? I like watering in level basins by flooding. But that requires a berm around the trees. You will probably need to use drip or spray nozzles if you plant on mounds or on top of a berm.

I will use the dripping line to make a circle within the raised bed. But as the tree grows bigger, should I move the irrigation outside the raised bed? We want the roots to eventually get down to the native grade, right?

Scott:

I can't say if you will need to irrigate an area larger than you raised bed. It depends on the size of the bed, size of tree, how much you irrigate, etc. Rainfall will eventually get the roots all thought the native soil. After all you do average 30 inches per year so the soil has to be wet at times. That will cause widespread rooting.

My experience with drip is that you need quite a few emitters per tree and frequent irrigation. I never was able to grow decent fruit that way. Hence my move to flood. But my soil is deeper and better suited to large applications. I apply at least two inches once a week during the dry parts of summer.

The best drip line is the one with built-in emitters. I use the 1gph emitters spaced at 24 inches. Basically with moderately permeable soil you need one emitter for every 2ft square of soil you want to wet. See below.

Here is a link that might be useful: drip works

This post was edited by fruitnut on Thu, Jan 3, 13 at 9:43

Fruitnut,

The raised will be 4X4X1 built out of landscape timber lined with landscape cloth on the inside.

The drip line I have is very similar to yours. It is made by Toro (called Toro Stripe Drip 1/4). You can find it in the orange big box store. It is 0.5 gpm per 6 inches.

Where are you located at? I may have received a free Hachiya persimmon from you about 5 years ago...

Scott:

I'm in Alpine in dry southwest TX. Don't remember anything about a persimmon.

May I ask why are you lining the bed with landscape fabric? I'd want the tree to root into the native soil. I big root system will make the tree more drought tolerant even during dry periods.

Try sheet multch. Basically, you alternate layers of organic matter, and top with good soil. An example would be:

Compost
blodd/bone meal
dried plant matter (leaves)
Peat
soil
newspaper
and repeat

IF the soil is as bad as it seems from your description, you can use plants that naturally "drill" into the soil (clover, asperagus, mustard, vetch, dandelion, daikon raddish etc.

You can mix in some species which naturally build the soil, such as clover, buckwheat, beans and peas (90% of legumes), or even some shurbs and trees like caregana, albezzia, locust, or redbud.

IF you need to build the soil fast, id recommend digging down 2 feet and loosening the soil, then tossing a foot of good soil ontop of the ground, and planting in that.

I've established orchards in shallow soils on many sites. the jack hammer method seems way too much work and if there are existing trees in the soil apparently there's plenty of soil for fruit trees.

A big problem is those trees already established which can greatly slow the establishment of new trees as their roots will find any loosened soil that is kept moist.

Trees can probably establish if you sever competing roots out about 4' from the trunk, perhaps creating a raised bed by scraping soil from outside this distance and throwing it to the center to form a bed. You can add some compost to the top 5 or six inches of soil of this bed and mulch with a heavy layer of wood chips. The scraped "moat" around the beds will discourage roots from the established trees.

Limited soil improves the quality of fruit. Especially in areas that get rain during the growing season.

Could someone comment on the practicality of my fig idea? These conditions are beyond my experience but I've seen figs grow in very rocky areas around the Mediterranean and when planted here the traditional advice was to fill the hole with rubble, or even line with paving slabs, to restrict the roots.

flora:

You are likely right about growing figs in the UK. Both grapes and figs seem adapted to poor dry soils. In fact the fruit has higher quality when not over supplied with water and nutrients. Thus the advice in your area to limit rooting. I'd imagine figs in the UK lack heat but have excess water due to your mild damp conditions, sort of like my greenhouse where it's easy to over water.