Gaura. The airy look of this three- to four-foot perennial (Gaura lindheimeri) comes from its long wiry stems bearing white butterfly-like flowers, sometimes with tinges of pink ('Siskiyou Pink' is bright pink). But the plant isn't as delicate as it looks. It's deeply rooted, grows in a variety of different soils (including alkaline) and is tolerant of drought. In many gardens, it seems to outcompete nearby weeds without becoming a nuisance itself. After a few years, dividing can get you more wonderful gauras. Hardy to USDA Zone 5.