In all my experience planting around a Cedrus deodorant Atlantica, I've never encountered mu h in the way of surface roots. The bigger issue will be the seed cones which fall constantly and can look messy or cat h between leaves of plants such as agaves or bromeliads. That's why I'd suggested grasses as a good choice, or fine textured foliage shrubs such as manzanitas. I'm willing to bet that a good long soaking over several days would make that area very easy to dig. Cedars in general are usually easy to plant around as the roots go deep.

I wouldn't fertilize, but I would consider amending the soil, especially if, as davidl_ny5 says, the soil is poor. You really can't add too much leaf mold to a soil that is intended to grow woodland plants, provided you can mix the leaf mold in with the mineral soil. If you don't have leaf mold- rotted leaves - you might check around with your town, township, or whatever local gov't collects the leaves in the fall. In most places there is either a program to compost the leaves and distribute them to gardeners, or perhaps just a place where leaves are dumped. In either case, you can probably get permission to collect rotted leaves for your garden. If you can get them work a foot of rotted leaves into the top foor of soil, then add another 6 inches on top and don't mix. If you can't manage this much, use a lesser amount. In either case, I think there is no substitute for rotted leaves when preparing a soil for woodland plants.

Identification of grasses can be very challenging. It usually requires close examination of the flowers, although some of the more common native prairie grasses can be identified pretty readily once you know what the overall appearance. A good starter book for grasses and grass-like plants is "Field Guide to the Grasses, Sedges and Rushes of the United States" by Edward Knobel. No photos, just illustrations and it doesn't distinguish between natives and non-natives. For other plants, something like Peterson's "A Field Guide to Wildflowers : Northeastern and North-Central North America" would be a convenient reference and it does mention which ones have been introduced.

Are you looking for evergreen or one that's bare part of the year? That's the BIG first choice. Cooking in the afternoon heat can be tough. - Lacey Oaks are EXTREMELY hard to find in larger landscape sizes in our area (Austin/SA) They're just not that well known and are SLOW. Larger specimens are usually only available from wholesale places. Here's a picture of some I looked at about an hour south of SA. Unfortunately I didn't have room for the Lacey on my trailer. These are 24in boxes. I opted for the even harder to find Canby Oak in 24in box. 24in Box Lacey Oak Nearly all the local nursery Lacey Oaks (not many) looked terrible. I may head back to get that Lacey next spring. Mexican, Bigtooth or Caddo Maples are all options but good luck finding any of those locally. I ordered all of mine and none bigger than 5g size. Bigtooth and Caddo are SLOW. Mexican Sugar is faster. Have you considered the Monterrey Oak (Q. polymorpha)? It's becoming common down here and seems to do very well. It's one of the faster growing oaks I've seen.