Colchicum bulbs (corms, actually) are so eager to grow that they'll bloom in their bag on a garden center shelf. Planted in soil, each bulb produces five or six flowers, which last for weeks. You'll often see colchicums referred to as autumn crocus, but they're a different species entirely.
Plant colchicums when the bulbs become available in August, for bloom just a few weeks later. Set them 3 to 4 inches deep, in full sun and in well-drained soil. Flowers will appear, but no leaves.
Colchicums are hardy to USDA Plant Hardiness Zone 5. Cultivars include the exquisite 'Waterlily', 6 to 8 inches tall; 'The Giant', up to 12 inches tall with lavender-pink flowers; 'Violet Queen', purple flowers, up to 7 inches tall; and C. autumnale 'Album', white flowers, 4 inches tall.