DAHLIA, a member of the Compositae family is a flowering plant. It is native to Mexico, Central America, and northern South America. Dahlias were cultivated by the Aztecs, taken to Europe by the Spaniards, and soon spread throughout the world in widely different climates. There are 18 species and thousands of hybrid varieties.
Dahlias are many-branched plants grown from underground rubbers. The stalks range in height from 10 inches (dwarf varieties) to 20 or 30 feet, but the usual height is from 1 to 8 feet. Flowers may be single or double. The petals are straight, rolled upward, and ruffled or flaring. Blossoms may be from 1 to 15 inches across. Colors range from white to nearly black and in all hues except blue. The petals often are flecked with another color. Blossoming time depends on climate, soil, and variety; it is usually from August until frost.
A sunny location and light soil are best for dahlias, but they can be grown in partial shade and in almost any soil that is not waterlogged. The tubers should be planted when the soil is warm, two or three feet apart (closer for dwarfs), and four inches deep. The plants need to be well watered, especially while blooming. It is helpful to fertilize before planting and again at the beginning of August. Stakes should be placed firmly in the ground before planting so that the stalks can be tied to the stakes when they are about two feet tall. After the tops are frozen in late fall, the tubers may be dug, cleaned, dried for a few days, and stored until spring. Dahlias may be grown from seeds, and dwarf dahlias can be grown indoors in winter.
Dahlias grow from tuberous, or thick, fleshy roots that look somewhat like bulbs. They should be planted in rich, well-drained soil and in full sun after all danger of frost has passed. After the first frost, the roots should be dug up and stored for the winter in a cool, dry place. Storing the root clump with soil attached will stop shriveling. At planting time, the roots should be separated and planted about 6 inches (15 centimeters) deep. Dahlias flower in the late summer.