Answer: If the site is sunny, you might try rockcress (Arabis), or one of the stonecrops (Sedum). Once established they take little water, and seem to be happy in poor soil. I've had good luck with sages, and Gaillardia under similar circumstances. You may even want to try one of the dwarf Lewisia's. They require excellent drainage, and I've found their root systems to be quite small.
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