There are several spring or summer flowers that are best planted as tubers, bulbs, pips, corms, or rhizomes. These are the Dahlias, Gladiolas, Canna, Lily of the Valley, Lilies, Caladium, Colocasia, and Alocasia.
Dahlias are tubers that are native to Central America and hardy in zones 8-11. They should be planted when soil temperature reaches 60° F in loamy organic soil. There are many varieties and sizes to choose from. The bedding varieties should be planted 9-12 inches apart and the large cutting varieties should be planted 36 inches apart.
Make sure your Dahlias are deeply watered at least weekly to keep them healthy. They require at least 6-8 hours of sun and prefer morning sun for best flower as the hot afternoon sun will burn the petal tips.
Once frost hits Dahlias dig them from the ground removing as much soil as possible without washing the tuber, let air dry and place in peat, vermiculite, or perlite in a cool 45°-50°F dry area to overwinter. You may divide the tuber if you have a few eyes with each division. Replant tubers in the spring when soil is at the correct temperature.
Gladiolas are wonderful cut flowers that grow from corms. They flower along long stems ranging from 2 feet to 4 feet in mid-summer. They should be planted once the soil temperature reaches 50°F in well-draining soil. Plant corms 2-6 inches deep depending on the height of the glad you are planting with taller varieties deeper. Plant in full sun in ensure the best flower. If you want gladiolas to flower all summer stagger the planting by 2-week intervals. Colors range from pure white to deep purple, almost black. The taller ones may need staking if not protected from prevailing winds. Like Dahlias if you want to ensure the corms survive, they must be lifted after the first frost and stored inside for the winter.
Many local fairs have been won with either Dahlias or Gladiolas. They make stunning cut flower arrangements.