Contrary to some claims that the dahlia is one of the easiest flowers to grow, there are several cultural practices that need to be carefully followed to grow them successfully.
Dahlias can be planted outdoors after the last frost in your area. In central Iowa, dahlias can be planted around May 10 to 15. Gardeners in southern Iowa can plant a few days earlier. Wait several additional days in northern areas. A frost or freeze can damage or destroy the plants.
Dahlias perform best in full sun and a well-drained soil. Avoid wet poorly drained soils as tubers may rot. Tubers radiate out from the dahlia crown like the spokes of a wagon wheel. Viable tubers must have an eye originating from the crown portion, plus a neck that connects the crown to the body of the tuberous root.
Before planting, drive a support, such as a metal fence post stake, wooden stake, or other device into the ground. Placing the supports into the ground prior to planting ensures that the tubers will not be impaled. Dig a hole on either side of the support. Place the tuber horizontally in the ground about 6 to 8 inches deep. Then place soil back in the hole. The dahlias should emerge from the hole in about 2 weeks. As the plants grow, carefully tie them to the support with yarn, thick cotton cord, or baling twine. Fishing line, wire, and other narrow materials should not be used as they can girdle the plant.
After the dahlias reach a height of 10 to 12 inches, plants need one inch of water per week throughout the remainder of the growing season. During dry weather, water the dahlias once or twice a week. Pull weeds as needed and enjoy fantastic blooms till frost.
This article originally appeared in the May 7, 1999 issue, p. 53.
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