Dahlias, discovered by Spanish conquistadors in Mexico and Guatemala during the 16th century, are prolific flowering plants that bring dramatic color to cut flower arrangements and gardens. The American Dahlia Society has developed classifications based on size, color and form, including stellar, pompon, cactus and peony. In addition to the intriguing shapes, an array of spectacular hues of white, yellow, red, orange, bronze, purple and variegated schemes exist. Blooms range in size from 2 inches to over 10 inches in width and some varieties grow to over 8 feet in height.
Fill containers with slightly moistened potting soil mixed with an equal amount of coarse sand. If the soil mixture is too wet, it will cause dahlia tubers to rot.
Sow dahlia tubers at a depth of 2 to 3 inches and cover lightly with soil. Swan Island Dahlias, a leading grower, recommends starting dahlia tubers at least six weeks before transplanting them outdoors in mid-April through May.
Place dahlia pots in a location that offers a temperature of at least 60 degrees Fahrenheit.
Transplant dahlias when they reach 12 inches in height.
Pinch back plants that are taller than 12 inches before transplanting them. Cut or pinch off the center shoot, directly above the third set of leaves.