The queen of phlox, this species is a tall perennial native to lightly shaded woodlands of eastern and central North America. Showy midsummer flowers grow in large, conical panicles, with hundreds of five-petaled blooms atop each two- to three-foot stem, from July to September. In hot, humid weather, mildew may develop on the leaves. Garden phlox is perhaps the most popular phlox used in the perennial border. Today, there are many superior cultivars on the market.