The term bulb refers to an underground storage organ that produces a plant. Rhizomes, corms and tuberous roots are all considered bulbs, reports the University of Illinois Extension. Flower bulbs can be either tender or hardy. Tender bulbs can not overwinter in the garden and must be dug up every fall and stored indoors. Hardy bulbs can remain in the garden year-round and will survive winter with proper care. A few examples of summer blooming bulb flowers are caladiums, canna lilies and dahlias.
Mostly planted for their foliage, caladiums have leaves that are heart-shaped and up to 12 inches in length. The foliage colors vary by cultivar, in a variety of reds, greens, whites or pinks. Caladiums grow from tubers started indoors and can be transplanted to the garden after danger of frost. They grow well in rich soil where they are protected from wind. Caladiums prefer shade, although some cultivars tolerate partial or full sun. These bulb flowers do not tolerate cold temperatures and must be dug up and replanted the following year.
Caladium cultivars include Cha Loum Pra Keat, Chang Suek, Hok Long, Jiao Ying, Ka La Houm, Khun Ying, Leung Pa Li Chart, Ma Had Thai and Lai Thai.
Cannas are a preferred bulb flower because of their long flowering period and striking foliage. The flowers come in a range of colors, including pink, red, yellow, cream and orange. Traditional cannas grow up to eight feet tall but dwarf cultivars are available as well. They can be planted directly into the garden in late May or started indoors in March. Cannas prefer well-drained soil and at least six hours of sun. Charles Behnke at Ohio State University Cooperative Extension recommends digging up the rhizomes after the cannas tops have died off from frost. They should be stored indoors at 45 or 50 degrees F.
Cannas cultivars include Light My Fire, Orange Beauty, Pfitzer Primrose Yellow, Richard Wallace, Scarlet Wave, Tangelo, The President, Tropical Sunrise, Wyoming, and Yellow King Humbert.
Dahlias can grow up to eight feet tall with flowers that span 12 inches across. They can be planted directly in the garden in May in a well-drained sunny location. Dahlias require a cool moist soil so mulching may be necessary. Insects can be a problem for Dahlias, so preventive spraying and frequent inspections are needed. Dahlias planted from seed are not heat-tolerant and will flower earlier with a smaller flower. Dahlia tubers grow in clumps that need to be dug up and stored over the winter months. The shape and color of the dahlia flower can vary by cultivar.
Dahlia cultivars include Snow Country, Vancouver, Blue Boy, Babylon Bronze, Babylon Purple, Tahiti Sunrise and Marble Ball.