Dahlia

Dahlias are the darlings of the late summer garden. Visit any county or state fair in the autumn and you will likely find dozens of dahlias. The array of flower colors, sizes, and shapes is astounding. Check out the American Dahlia Society website for the many classifications and colors.

There are 42 accepted species of dahlias available in almost any color:  white, shades of pink, red, yellow, orange, shades of purple, and various combinations of these colors. Some of the flower forms are truly amazing, from the charming single, daisy-like flowers to the popular double varieties which can range from the 2-inch-pompons to 12 inches across. They are divided into ten groups: single, anemone, collarette, waterlily, decorative, fall, pompon, cactus, semi-cactus and miscellaneous.  Some of the most spectacular are the peony and cactus forms.

Any garden with fertile, well-drained soil and lots of sun can become a home to dahlias. Since all garden dahlias are hybrids, they are most often planted as tuberous roots. Seeds are available for mixed, small-flowered types. Plant the tuberous roots or plants about the time of the last frost date, 1 to 3 feet apart depending on the variety. They look best planted in groups of at least 5.  Varieties that get taller than 2 feet may need stakes or other supports. Dahlias may languish during the heat of summer, but keep them mulched and provide plenty of water and they will reward you with a show from late summer through fall to first frost. Deadhead spent flowers to extend blooming.

Dahlias are herbaceous perennials, but typically grown as an annual. The tuberous roots will not survive winter in the ground in most of the Piedmont region and the western part of the state, so those of us in these regions must be prepared to dig roots in the fall to store during the winter. The dahlia is hardy in the Raleigh area and east to the Coast.

When planting, cover tubers to a depth of 3 inches. Note that these plants can be injured at temperatures below 25 degrees F (2 degrees C). When grown from tubers, dahlias tend to be tall and may require staking. Dahlias can also be grown from seed-germinated selections but these are typically dwarfs and often not heat tolerant, lack uniformity of growth, and are poor bloomers.

Insects, Diseases, and Other Plant Problems:  They can be difficult to grow and suffer from many problems including aphids, leafhoppers, and caterpillars.  Potential diseases include powdery mildew, root rot, crown gall, viruses, and wilts.  This plant may cause contact dermatitis in some people.  

VIDEO Created by Elisabeth Meyer for "Edibles, Bulbs, and Houseplants" a plant identification course offered in partnership with Longwood Gardens.