Summer bulbs, sometimes called tender bulbs, combine the best characteristics of annual and perennial flowers. Like annuals, summer bulbs have a long season of bloom; like perennials, they deliver year after year of service.
In Northern gardens, summer bulbs must be dug up and stored each fall. In frost-free areas, they can be left in the ground all year long.
The flowers of ranunculus look as if they're made of crepe paper. Available in both single- and double-flowering varieties, blooms range in size from 1 to 4 inches wide. Most impressive are the double blooms, which are solidly packed with petals. Ranunculus blooms in a wide palette of colors, including white, red, yellow, orange, and pink. Newer varieties offer the largest flowers and the full color range. Reaching heights of 12 to 14 inches, the lush blossoms start appearing in July and August. Each ranunculus bulb produces six to eight flowers at intervals of one or two weeks, so you'll have lots of flowers for show and cutting.
Start ranunculus indoors in a greenhouse in the late spring, or set them directly outdoors when the danger of frost has passed. Soak the stiff, dry tubers in warm water for several hours before planting to encourage sprouting. Set the tubers 2 inches deep with their points pointing down. Ranunculus demands plenty of sun and a fertile, well-drained, but not continually dry, location. Group 10 to 20 bulbs together in the same spot for a bold show of bloom. In the fall, after the foliage has died back, lift the bulbs. Store them through the winter in boxes of sphagnum peat moss or perlite in a cool, dry location that stays 50 to 55 degrees F.