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Care for Dahlias

By M.H. Dyer ; Updated September 21, 2017
Colorful dahlias add variety to the flower bed.

Dahlias may require a bit of tender loving care, but the graceful flowers, which will bloom from midsummer until the first frost, are well worth the extra effort. Dahlias are available in sizes from dainty pincushions and pompoms to giant dinner-plate-sized blooms, in both graceful single daisy-like blooms and fluffy double flowers. Dahlias will be sure to add variety to the flower bed, in a rainbow of hues ranging from red to yellow to purple to red and all shades in-between.

Purchase high-quality dahlia tubers. Although good tubers may be expensive, they will result in stronger plants and larger blooms.

Plant dahlia tubers 12 to 24 inches apart where the dahlias will have at least six to eight hours of sunlight every day. If the soil is poor or doesn't drain well, work 2 to 3 inches of rotted manure or bone meal into the top of the soil. Plant the dahlia tubers horizontally, about 4 to 6 inches deep. If you see visible "eyes," or growing points, plant the tubers with the eyes facing up.

Keep the soil moist but don't water excessively. Soggy soil can damage the dahlia tubers and roots.

Fertilize dahlias once each month, with the last feeding in August. Use a fertilizer with a low nitrogen content, such as a 5-10-10 fertilizer, applied according to the recommendations on the package label. Too much nitrogen will result in bushy foliage but few blooms.

Pinch off the main stem of the dahlia plant when the plant has three to four pairs of leaves. Pinching off the main stem will cause the dahlia plant to grow two main stems, resulting in a bushier, fuller plant and more blooms.

Remove side buds that grow adjacent to the main bud on each stem. Removing the side buds will allow one primary bud on each stem to grow much larger, and will also result in longer stems, making the dahlias easier to use in cut flower arrangements.

Stake large dahlia varieties when they reach 12 to 15 inches. Drive a wooden or bamboo stake into the ground and tie the dahlia to the stake with soft fabric or a strip of torn pantyhose. Leave a few inches between the stake and the plant so the tubers won't be damaged by the stake.

Dig the dahlia tubers for winter storage after the first frost of the season. Cut the dahlia plant down with pruners, leaving a 4- to 6-inch stem. Insert a garden fork into the soil about 12 inches from the plant so you don't damage the tuber, then repeat as you dig completely around the plant. Work carefully, as the tubers can crack or break.

Rinse the dahlia tubers with a garden hose, using a gentle spray. A strong stream of water can wash the protective skin from the daisy tubers. Set the tubers aside to dry for 30 to 40 minutes, then store the tubers in a plastic or cardboard box filled with vermiculite. Store the dahlia tubers in a dark room where the temperature will be maintained between 40 and 50 degrees Fahrenheit.

 

Things You Will Need

  • Dahlia tubers
  • Rotten manure or bone meal
  • Fertilizer with low nitrogen content
  • Wooden or bamboo stakes
  • Soft fabric or strips of pantyhose
  • Pruners
  • Garden fork
  • Plastic or cardboard box with lid

Tips

  • Don't be in a hurry to plant dahlias. The tubers won't grow until the soil warms to at least 60 degrees Fahrenheit.
  • If you're storing several varieties of dahlias, write the color and variety of dahlia directly on the tuber, using an indelible pencil. Indelible pencils can usually be purchased in office supply stores.

About the Author

 

M.H. Dyer began her writing career as a staff writer at a community newspaper and is now a full-time commercial writer. She writes about a variety of topics, with a focus on sustainable, pesticide- and herbicide-free gardening. She is an Oregon State University Master Gardener and Master Naturalist and holds a Master of Fine Arts in creative nonfiction writing.