You cannot plant a tree if bedrock is 6 inches below the soil. In fact, you cannot even plant grass, unless you water all summer. After I had a tank installed to provide water when the lines from the gravity feed spring freeze sometimes in winter, I couldn't grow grass over it because it was only a few inches below the surface. I gave up and now grow sedums there.

The worst (hottest) sun is the late afternoon/early evening summer sun. So a tree to the southwest is what you want. Yes, it's nice to block that morning sun too, but if your geology is correct, you can't plant one.

What's that presumably invasive juniper or cedar I see growing on the blasted rock "canyon walls" bordering my interstates from here to southern Missouri? Maybe it will do.

Cracks in vertical rock not the same situation as a horizontal layer of rock near the soil surface.

Bryan,

Look around to see what's already growing in the vicinity. Bet there are some that are handling it.

I've planted persimmon seedlings over sandstone bedrock, with less than 6" of soil - heck, I had to use my spudbar to bust a big enough hole to get the 1-gal pot rootball below grade. 16-18 years later, they're growing fine, producing bumper crops of fruit. Yeah, they're smaller and slower-growing than some just 40 ft up grade that have more soil to grow in, and I'd bet if you could see an X-ray photo, that their roots are ranging far away...and crawling into cracks/crevices in that rotten sandstone slab.

Whatever you plant, I'd recommend you start with something SMALL/young. Persimmon, shagbark hickory, scarlet oak...all tend to be found here on rocky partially erosed hillsides with thin soil. The'd be worth a try.

Living as I do in a region similar to that described, the issues are: Soil pH is apt to be on the high side. Select plants able to handle high pH. Some species actually prefer this condition and like the easy access to calcium/magnesium. Soil depth. Sure, if there's in fact a solid layer four or six inches under the surface, planting will be difficult. Yet nature would plant such a spot with ease. So I second the notion to look around you and see what's working. And if it is in fact a solid layer, as opposed to a broken up and fractured thing, that will influence the size of plant you can install. Water. Such a site may be very wet-an induced high water table, or, it may drain rapidly, via cracks in the karst bedrock (if present). You will have to pay attention to how rapidly things dry out.

Lots of plants can handle these situations. Start by observing. And while probably not native to your area, Thuja occidentalis actually prefers sites like you describe. Many places in NE WIsconsin -this tree is surviving and thriving on little more than straight dolomite (limestone) rock, especially in the vacation wonderland of Door County, where numerous examples can be seen growing on cliffs, etc.

+oM

Personally I would rather have a shagbark hickory, persimmon, or scarlet oak, however, another choice is Platanus occidentalis.

Do as suggested and start small.

Dax

You know I got to thinking and another (not fast but not slow) option is Acer truncatum. There are grafted selections that are pretty cool such as A.truncatum 'Fire Dragon'.

Dax

Thanks for the advice. It's hard to tell what trees are thriving under these soil conditions in the area except for along the interstate I see a lot of cedars on the limestone. I do know that this particular area I'm looking at is solid rock--we had some grading issues on that side of the house and it cost a small fortune to fix that and install a proper draining system. If I can get a tree established, I'm worried the roots won't have anywhere to go but towards that draining system or my house.

Many trees grow in the rockiest soils -- oaks, hickories & many pines for example.

Nature colonizes such sites with relative ease. Us gardeners-not so much. Sounds to me (from a distance) like maybe a groundcover or spreading perennial planting of some kind might take hold better in the near-term. Then maybe later, things will have softened up enough to allow for seed-grown trees and/or shrubs to take hold. I'm really talking about planting seeds. In a stressful environment, even the smallest of transplants will immediately be out of synch with its surroundings, whereas a seed-grown plant will never grow one iota more than conditions allow. That's why you see trees growing in cracks in solid-rock cliffs, along waterfalls, etc. although in the latter case, spray from the waterfall helps too. My point being that, a big potted, B&B or other plant, introduced to that situation, will probably struggle at best, while something grown from seed just might work.

+om