Corydalis Flexuosa "Purple Leaf"This C. is expensive to buy (we paid $12 for the original 4" pot of this parent plant). This is not the common "Blue Panda" or "China Blue" which have solid green leaves -- this has a little reddish/purple dot on each leaf -- I don't remember the exact name. It spreads slowly but steadily over a few years. It's not real drought tolerant, be sure it's not too far from the drip hose.
Yellow Fern Corydalis (C. Cheilanthifolia)This version of Corydalis is difficult to find, but easy to grow. It'll spread by throwing out a few new plants, but can be easily controlled by simply yanking out the little plants. Breaking off a small chunk of the plant and stuffing it in dirt will cause it to root easily. Plants get up to about 10" high, about 8" around.