Dahlias are one of the most colorful plants in the garden in late Summer and early Fall. They are not difficult to grow and make a beautiful display of indoor cut flowers with very little arranging required. They come in every imaginable color except blue. Their flower size varies from 2 inches to a foot across (called dinner plate!). Plant height can range from less than a foot to 8 feet. There are over 9,000 different varieties of dahlia, a member of the Asteraceae family. Each variety is classified by size and form; forms include, Cactus, Waterlily and Ball. For more details on dahlia classification, check out the information on the American Dahlia Society’s web site.
Buying and Planting
Dahlias are usually purchased as tubers in late Winter or early Spring. They also may be purchased and planted as cuttings, which will develop tubers underground during the summer. There are many online vendors offering a dazzling display of various colors and shapes of dahlias. Dahlia societies, also accessible online, offer lists of the best growing and showing dahlia varieties.
Expert growers often plant tubers in shallow trays or temporary pots for an early growing start. In the Shippan area, because the threat of a late frost is minimal, tubers can simply be planted in place in late March as long as the soil is not soggy. Late April or early May is the more usual planting time because Spring rains and overly wet soil can rot the tubers. Plant in good tilled soil with a fair amount of compost in a shallow hole 4 to 6 inches deep, allowing about 3-4 feet between plants. This is the time to tag with the variety name and to place stakes for the expected height at maturity. Of course, small varieties take less space. Dahlias may also be planted in large pots if well staked. It is not advisable to water dahlia tubers until leaves appear above ground.
Dahlias respond well to feeding. Incorporate a good 5-10-15 or 5-10-10 fertilizer according to the instructions when planting. Especially when grown in pots, extra feeding may be required.
Topping and Disbudding
In order to get the best shaped plant and the most flowers, topping the plant (pinching out the center) is recommended when 3 to 6 pairs of leaves have been produced. Lateral stems will then grow and each produce flowers and leaves. Once buds are produced, they will have small side buds which should be carefully removed (disbudded) to give the center bud a chance to produce a larger bloom.
Cutting flowers, to enjoy in your home or to give as gifts, is one of the joys of growing dahlias. It is also good for the plant to use its energy to produce additional blooms. Cutting early in the morning is best since that is when the bloom is most hydrated. A fresh cut underwater and replacing cloudy water will extend the life of cut flowers as will floral preservative. With care, a cut dahlias will last 8 to 10 days after being cut.
Digging and Wintering
Once there has been a killing frost and dahlia leaves have blackened, they may be dug for winter storage. Cut the plant off so that about 6 inches of stem remains and wash dirt off the tubers. To retain the name of the dahlia variety, tag it or write the name right on the tuber with a permanent marker. There are a variety of ways to store dahlias (in newspaper, peat moss and cardboard boxes) which you may review elsewhere online. But the critical thing is that they must be kept cool without freezing. If the dahlias are grown in containers that can be moved, depending on basement conditions, they may simply be left in the container and placed in a basement, and maybe given an occasional sprinkling of water. In the Spring, the tubers can be divided to grow multiple plants.
Many experts feel is is better to divide them in the fall. Splitting the dahlia tuber then has the advantage that only the best tubers need to be stored, and individual tubers can be removed from storage if they deteriorate.
Look For The Dahlia ‘Eyes’ or Growing Points. There will be several ‘eyes’ or growing points on the dahlia tuber and it is important to identify these. A tuber will not sprout unless it has at least one “eye.” The eyes are typically found at the top of a tuber on the ridge where the tuber joins the stem. When a tuber is removed from the clump, the ridge containing the eyes must be attached to the tuber. In some cases, this will require taking a piece of the stem as well. Not all tubers have “eyes.” If a tuber has no visible eye it will probably produce an eye next spring when it is moistened and warmed, then again it may not. Try to save the tubers with visible eyes first. Save the doubtful ones later or discard them. Tubers without eyes may grow roots, as tubers with eyes do, but they will not sprout.
The tuber from which the dahlia plant grows (referred to as the “mother” tuber) sometimes rots and dies and sometimes it lives on. The mother tuber is often darker than the surrounding tubers, Sometimes it may have an eye, but it is best to throw this away. Reject tubers if the necks are thin and easily broken, these may well rot in storage.
The many dahlia growers may be found online by googling “Buy Dahlia tubers”. Also look at Web sites of various dahlia societies. There is a “Fabulous 50” list of dahlias all of which have won many blue ribbons in competition. Selecting varieties from this list will help assure that you are picking some of the best dahlias to grow in your own garden.