I happen to have a thing about rocks/boulders also. I've brought home nice rocks or boulders from other areas...also some shells. Not too crazy about the softer limestone that I sometimes find when digging around here, however. I have quite a few species of native Texas plants that do quite well on my place. The very extreme droughts in the last five years have brought home the value of xeriscape plants. It's just not worth it to try to grow wholly inappropriate plants that need tons of water!
