How Deep to Plant Dahlia Bulbs

Dahlias grow in a profusion of colors, shapes and sizes.

From mid-summer to first frosts, dahlias provide blooms in a profusion of colors, shapes and sizes, ranging from 2-inch pom-pons to 12-inch or wider "dinner plates." Instead of bulbs, dahlias grow from tuberous roots that store nutrients.

Propagation

Dahlias are propagated from seeds, cuttings or tuberous roots, depending on the type of dahlia, but they are commonly grown from tubers. Plant dahlia roots that have one live bud or eye, which is in the crown area. Divide the roots at that location with a sharp knife or pruning shears.

Planting Depth

A ball dahlia has a different type of bloom.

Plant dahlias in holes 8 to 10 inches deep and wide enough to accommodate the roots. Loosen soil at the bottom of the hole and refill it to a depth of 6 inches. Place the tuberous root on its side, with the eye facing upward, and cover with 2 to 3 inches of soil. Fill in soil around each plant as it grows, until the surface is level.

Planting Location

Dahlias require a minimum of five to six hours of sunlight daily and well-draining soil. Because dahlias are heavy feeders, spade the bed to a depth of as much as 8 to 10 inches before planting. Work in comport or manure for a slow release of nitrogen. Also work in 5-10-15 or 5-10-10 fertilizer. If soil tests indicate low pH, add ground limestone.

References

• University of Minnesota Extension: Growing Dahlias
• University of Illinois Extension: Bulb Basics
• North Carolina Cooperative Extension Service: Dahlias for the Home Landscape
• Cornell University Home Gardening: Dahlia, Medium to Tall Varieties

Resources

• University of California Integrated Pest Management Program: Dahlia---Dahlia spp.