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.
Electrify shady spots in your garden with tuberous begonia. These versatile beauties bloom in vibrant colors such as red, pink, yellow, orange, and white and in a wide assortment of flower forms. They are available in upright and trailing varieties, and give you the choice of double and single flowers. Choose upright varieties for pots, edgings, and borders, and use trailing types atop low walls and in hanging baskets. Best of all, tuberous begonias are perfect for containers, so you can place them where you need color the most and move them out of locations that receive constant, harsh sun. Although most tuberous begonias must be lifted in the fall and replanted in the spring, one species, Begonia grandis, tolerates moderately cold winters with a good layer of mulch.
To start tuberous begonias, buy hard, round tubers in April or May and place them in a low flat filled with sphagnum peat moss. Be sure to set the tubers round side down. Place the flat in a bright location and when the begonias are about 3 inches tall, move them to soil-filled containers. In the South, you can plant the tubers directly in the ground once the soil has warmed. Place tubers in a hole 2 to 3 inches deep and cover them with soil. A partially shady location is best. Neither deep shade nor full sun is recommended. Be sure to keep begonias well watered. For striking color, plant three to five tubers in the same location.
If you want your begonias to bloom again next summer, dig up the tubers, remove the soil around them, and clip away the foliage before the first frost.
The wet marshy areas of South Africa are the home of zantedeschia, the calla lily, where its ubiquitous appearance has earned it the name ditch lily. Everywhere else in the world, however, the elegant calla lily is held in high regard. From the Greek word meaning "beautiful," the lovely calla lives up to its name. The shapely spathes are rich and velvety, looking more artifical than flower.
Loving moist, nearly swampy places, the larger callas are good border plants for water gardens and will grow even in shallow standing water. Smaller calla species grow well in borders, beds, and containers. In areas free of killing frosts, callas will stay green all winter. Known primarily as a greenhouse or indoor plant, the calla lily deserves more recognition as a tender outdoor bloomer, happy in full sun or light shade. Mature plants grow 24 inches tall and are available in white, yellow, or rose, depending on the species.