Nursery Market Report: Aug. 2000, Dahlias

Offering long-lasting blooms and brilliant colors, dahlias add drama to a landscape from early summer until frost.

Extensive hybridization has led to countless forms. Heights range from 8 inches to 7 feet, flower sizes are 2 to 12 inches and colors cover the rainbow.

DAHLIA CHOICES. Ball Floraplant offers three new colors in its ‘Dahlietta’ series. Each plant is crowned with double flowers. ‘Dahlietta Mandy’s’ petals show a contrast of purple with a small, white, tubular floret in the middle and a yellow center in each bloom. ‘Mandy’ is naturally compact with mildew-sensitive, dark green leaves. ‘Dahlietta Anna’ features a new scarlet color, and ‘Dahlietta Susanne’ has pale pink blooms that deepen in color when light intensity increases. Both have compact growth habits.

GroLink Specialties offers 13 choices in its Gallery series and is developing several new ones. Bicolor choices from the series include ‘Art Deco,’ which is orange with a deep red heart and 4-inch flowers, and grows to 12 inches.

Other options in the series are named after famous artists. ‘Cézanne’ is canary yellow with 3-inch flowers and grows to 10 inches. ‘Salvador’ is light pink with a darker heart, medium pink striped petals, 4½-inch flowers and grows to 12 inches. ‘Vincent’ is orange with a darker heart, 3-inch flowers and grows to 10 inches.

PLANTING POINTERS. Follow this advice from North Carolina Cooperative Extension, Raleigh, N.C.

• Plant in warm, well-drained soils in spring.
• Select a location that receives at least six hours of direct sunlight.
• Incorporate 2 to 4 inches of compost, pine bark or manure and 2 to 4 pounds of 8-8-8 or 10-10-10 fertilizer per 100 square feet before planting.
• Dig a hole 8 to 10 inches deep and wide enough to fit tubers. Refill to a depth of 6 inches. Set the root on its side with eyes facing upward. Cover with 2 to 3 inches of soil and gradually fill in around plants until the surface is level.

DAHLIA CARE. After plants are established, a deep watering once or twice a week is necessary during warm, dry weather. Watering too early will increase the chance of rotting tubers. In drought conditions, soak growing plants with at least 1 inch of water each week, wetting the soil to a depth of 1 foot.

Use a water-soluble fertilizer monthly, or apply 2 to 3 pounds of 5-10-10 or 10-10-10 fertilizer per 100 square feet in July. A second application may be needed on sandy soil or during rainy seasons.

Dahlias’ tuberous roots produce multiple shoots. While shoots can be left to grow, thinning produces higher quality flowers. Leave one to four of the strongest shoots.

When plants are about a foot tall and the chosen stalks have grown three or four sets of leaves, pinch out the terminal shoot to encourage branching. This forces lateral shoots at each leaf node to grow and makes plants bushier.

Disbudding increases flower size. When the three buds that form at the end of each branch reach the size of small peas, remove the two side buds. Small-flowering types should not be disbudded.

Dahlias that reach more than 3 feet tall can topple in the wind. Placing a stake in the hole at planting time provides support without damaging tubers.

PESTS AND DISEASES. The most common pests are aphids, spider mites, leafhoppers, thrips and European corn borer. Slugs, snails and earwigs are best controlled

by trapping or hand picking. Likely disease problems include tuber rots, ring spot, vascular wilts, mosaic virus, powdery mildew and botrytis blight. Problems can be reduced by following recommended cultural practices and providing good air circulation.

For more information on specific dahlia cultivars, visit the American Dahlia Society web site at www.dahlia.org.