Dahlias are the queens of the late summer garden, lasting until the first frost, with abundantly shaped and colored flowers on plants very short to 6’ tall. They make a garden—which may be looking tired from a lot of summer work—look new, colorful and lush, while also providing flowers for fantastic arrangements in the house.
Dahlias are native to the mountains of Mexico, Columbia and Guatemala, where they grow as “trees.” Dahlias are perennial there, and are the national flower of Mexico. They are members of the same family as asters, sunflowers, daises and zinnias. Conquistadors brought dahlia seeds to Spain in the 16th century, but the real hybridizing got underway in Holland in the mid-19th century and has continued energetically ever since. At present, there are 18,000 varieties of dahlia!
Dahlias are classed by flower size and shape—and there are many. A perusal of a good dahlia catalogue like Swan Island Dahlias can cause much over-buying by the dahlia lover as it becomes necessary to have that one…and that one…and—wow—that one, too!
Several of our local garden centers offer dahlias, but in limited varieties. If you want something other than the general crowd pleasers (and these ARE pleasers), you are going to need the catalogue. Fortunately, dahlias are easy to grow from tubers.
Dahlias like to be planted in warm, loamy soil—that is, at least 60°—and in full sun. If you can provide these conditions, you can grow dahlias—no special skills are needed. Complete planting instructions come with your order so I won’t describe them here…too easily forgotten by spring.
If you have them in your garden, you have undoubtedly found out that they need to be staked—even some of the shorter ones need support, and especially those 4’ and taller. And your stakes need to be substantial. In a cutting garden I tend, which is tucked out of sight of the rest of the landscape, I use three tomato cages around one dahlia. I tie the cages to each other, which makes them very stable and provides ample places to tie branches. The owner of this garden cuts flowers regularly, which helps keep the plants growing in a good shape. In another garden I tend where dahlias are the end-of-summer garden feature, I stake them with two 6’ bamboo poles per plant. Tying the plants in this configuration is a challenge, but this garden owner also cuts often, which helps the plants stay bushy.
Dahlias cannot live through our winters here (although I know of one that does!), but they can be lifted, stored, and replanted. After the first good frost, or in mid-November if there is no frost, the foliage will begin to blacken. Cut the stem to 2–4” and gently lift the clump with a fork. The tubers are minimally connected to the main clump and can break off easily. Start farther away from the stems than you think you should because the clumps can be very large at this time. Carefully remove as much soil as possible. Do not wash the tubers. The clumps can be divided at this time, or in the spring. You must use a sharp knife and be sure that each tuber has an “eye.” Practice makes perfect.
Store the tubers in temperatures of 40–45 degrees, in a newspaper-lined cardboard box. Layer them in damp peat moss. Never store them in plastic containers or bags. During the winter, check them monthly to be sure none have rotted and the moss is still damp. Next spring, the process will begin again.
Then again, you can always just buy new tubers in the spring and try some different varieties of dahlia.
Jeanelle Myers is a professional gardener, landscaper and consultant. For gardening discussion you can call her at 631-434-5067. jeanellemyersfinegardening.com