of the month
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(DAL-ya, DAHL-ee-a or DAY-lee-a)
Flower forms on Dahlias are variable, with one head per stem. Flower diameters range from 4 to 10 inches. The stems are leafy and are 12 to 24 inches long. The American Dahlia Society categorizes Dahlias into 20 groups based on size, form and color: Anemone, Ball, Miniature Ball, Collarette, Incurved Cactus, Semicactus, Straight Cactus, Formal Decorative, Informal Decorative, Laciniated, Novelty, Novelty Open, Novelty Fully Double, Orchid, Peony, Pompon, Single, Mignon Single, Stellar and Waterlily.
The American Dahlia Society recognizes 15 colors or color combinations of Dahlias, including white, yellow, orange, pink, dark pink, red, dark red, lavender, purple, bronze, flame and bicolors.
Potted Dahlias can be displayed in bloom for four to five weeks, depending on variety and the care they receive.
Dahlia plants are available from April through November.
in-store and consumer care
LIGHT Bright, indirect light is recommended for Dahlias that are displayed indoors. Inadequate light levels can result in spindly stems and thin leaves with few or no flowers.
WATER Keep the plants moist at all times, but do not allow standing water, or the roots will rot.
TEMPERATURE Dahlia plants require moderate temperatures to grow and flower. A temperature range of 65 F to 80 F will satisfy the need of most hybrids. Lower temperatures during blooming will make the flowers last longer. The plants should be stored at temperatures no lower than 55 F.
HUMIDITY Dahlias prefer moderate humidity levels.
FERTILIZER When plants start growing, work about 1 tablespoon of complete plant food into the top inch of soil. Feed the plants every two weeks in slowly increasing amounts. Don’t use high-nitrogen plant foods, which will cause the stems to become soft and the plants to grow leaves at the expense of flowers.
GROOMING Remove individual flowers as they fade. If lower leaves turn yellow, they can be removed without damaging the plants.
ETHYLENE SENSITIVITY Dahlias are moderately sensitive to ethylene gas. Check with your supplier to make sure your plants have been treated at the grower or transportation level.
PESTS Wash off any spider mites, aphids and mealybugs with insecticidal soap. You also can dab rubbing alcohol directly onto mealybugs with cotton swabs. Snails also are attracted to Dahlias; simply remove them.
WHAT'S IN A NAME Dahlias are named in honor of Swedish botanist Anders Dahl (1751-1789), a student of famed botanist Carl Linnaeus.
FAMILY Dahlias are members of the Asteraceae (Compositae) family. Relatives include chrysanthemums (Dendranthemas), Calendulas (pot marigolds), Cosmos, strawflowers (Helichrysums) and Zinnias.
HOME SWEET HOME Dahlias originated in the mountains of Mexico, Central America and Colombia. They were discovered there in the 1500s by Spanish conquistadors, who took the flowers to Spain.
HISTORY The first Dahlia breeders were more interested in a food source than an ornamental crop because the blooms then weren’t noteworthy and Europe’s potato crops were failing. However, Europeans disliked the roots’ taste. By the early 18th century, new varieties had been bred, and the first fully double forms began to emerge.
Some information provided by:
The American Dahlia Society, www.dahlia.org
Brannan Street Wholesale Florist; San Francisco, Calif.
Chain of Life Network®, www.chainoflifenetwork.org
The Garden Helper, www.thegardenhelper.com/dahlia.html
Plant Ideas, www.plantideas.com
Reach “Blooming Plant of the Month” writer Steven W. Brown, AIFD, at email@example.com or (415) 239-3140.