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.
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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, which grows 6 to 8 inches tall; The Giant, which grows up to 12 inches tall with lavender-pink flowers; Violet Queen, with purple flowers, which grows up to 7 inches tall; and C. autumnale, or Album, with white flowers, which is only 4 inches tall.