Alliums burst into glorious spheres of bloom in late spring, as jaunty and debonair as the season. Fall is the time to plant them by the dozens…. Have fun with them. “I have a favorite, and it is Allium schubertii,” says Barbara Katz, a garden designer in Washington, D.C. “It’s like a constellation.” Allium schubertii is an atypical allium, growing on stems only about 18 inches tall. The globe of blooms, on the other hand, is about 12 inches in diameter. Individual flower stems are of several different lengths: The effect is distinctly starlike, twinkling madly. Katz also plants “a ton of Purple Sensation” alliums in her own and clients’ gardens. The dark purple blooms stand about 30 inches tall. “I mix it with hostas, and it looks like the hostas are flowering,” Katz says. “I plant it around hydrangeas. It’s fun.”