Like most hardy bulbs, alliums are best planted in early fall, but you may get away with planting them in early spring if you can store them in a cool, dry place. Another option is to plant them now in a large container and place it outside or in an unheated garage so they will get enough chilling to bloom. Make sure the soil around them stays slightly moist but not waterlogged.
Some other hardy summer-flowering bulbs to consider include Sicilian honey garlic (Nectaroscordum siculum) and native spider lilies such as Hymenocallis caroliniana and H. liriosome, which are hardy to USDA Zone 7. �Crinum lilies would be really good for Chapel Hill,� says Nancy Goodwin, creator of Montrose gardens in Hillsborough, North Carolina. Crinums and spider lilies have an advantage over some other summer bloomers in that they don�t mind clay soils, and some even thrive with wet feet. Despite references that indicate these bulbs are hardy only in Zone 9 or 10, Goodwin has had no problem growing Crinum �Ellen Bosanquet�, C. �Milk and Wine�, or Amarcrinum memoria-corsii, a hybrid between Amaryllis belladonna and Crinum moorei. Good choices for lower-growing bulbs, according to Goodwin, are rain lilies such as Zephyranthes candida, Z. flavissima, and Habranthus robustus, which flower after rainfall throughout the summer. Old favorites include Gladiolus, Crocosmia, and, of course, many, many lilies (Lilium spp.)