By Susan Silverman ©2014
I love to walk the perimeter of my landscape and visit with all the blooms and woodies. There is so much anticipation and joy when each cultivar begins to emerge, I leave the garden intact, cutting nothing, so I can visit and revisit the beauty that occurs early, mid and late season. There is one exception, the dahlia, a flower that begs to be brought inside so that it can be admired 24/7. The dahlia is the queen of fall.
When a flower is this spectacular, you know that it is a high-maintenance diva. Do what she demands and you will be richly rewarded with blooms from July through October. When the early and midseason perennials have withered, browned and bloomed out, the dahlia comes alive and brings intense color and nonstop flowers that end the season on a high note. This is a flower that must be shared with friends and family.
A vase filled with dahlias is pure joy. If you wish to bring them inside, cut them early morning and immediately place the stems in a bucket of hot water to prolong the life of the flower. Cut buds will never open, so take fully mature blooms. Strip all the foliage left on the stem and recut it to fit your vase. Change the water daily. The dinner plate-size dahlias do not hold up as well as the smaller varieties, and the ones with open flat faces, the anemone type, tend to lose their petals quickly.
Dahlias are not a hardy perennial in our zone, so your choice is to compost or overwinter them and plant them again next spring. This recycling process is not difficult, but you must be patient. Tubers dug too early will never harden and hold up in storage.
When a hard frost blackens the foliage, the time has come to begin the process. The extreme cold ripens the tuber and makes it ready for harvest. Dahlia experts say that if we don't get a killing frost by Thanksgiving, dig them up then.
Cut off all the foliage above ground to about 4 inches, then carefully dig out the underground mass. The dahlia that was planted in the spring has grown exponentially, so place your spade at least 6 to 8 inches away from the plant. Hose off all the soil and place the dahlias in a shaded, protected place to dry.
At this point, you can divide the tubers, which look like little yams growing out and around the stem. Discard any that are soft and broken. It is best to discard the “mother” tuber, which was the original plant. It is easy to identify because it is coarser and darker than the others. It has used its energy to create all that surrounds it. Only save the tubers that have eyes. These are the whitish/pink dots on the tuber that are located where it is attached to the stem. They look like small pimples. These eyes are where next year’s stem will arise. Tubers without eyes will never be viable.
I store my tubers in cardboard boxes that are lined with several layers of newspaper. Fill a bucket with peat moss and mix it with very warm water. Continue to wet and stir the peat moss until it has the consistency of a damp sponge. Place this mixture on top of the papers, then add the dahlias. Cover them with more peat moss. You can continue to layer in this fashion by adding additional tubers and then peat moss. At this point your dahlia torte will be ready to put in hibernation. Store the box in a cool, dry place. A root cellar with a temperature of 50-60 degrees is perfect. If it is too cold, the tubers will freeze, and if it is too warm, they will shrivel. Label the variety in the box.
After winter has passed and the daylight hours begin to grow longer, you can unpack the tubers. Discard any that are shriveled or soft. I like to jump start my dahlias by potting them in a soilless mix. This can be purchased at any hardware store or nursery. I do this by the end of March or the beginning of April. Move them to a warm, well-lit location and water them sparingly. I feel that placing these established plants in the garden will make for a longer season of growth. However, if you choose to plant the tuber directly into the garden, do this only after the ground temperature has warmed to 60 degrees. The old rule was to plant after Mother’s Day, but rules are not commandments. Plant the tubers or small dahlia plants only when there is no longer a danger of frost. This extreme cold is a sure killer and a sad end to all your efforts.
Dahlias require two things: abundant sunlight and soil with good drainage. If positioned in partial shade, they will grow tall, unwieldy and fail to flower well. They are reaching for light. Do not water newly planted tubers; excessive water can lead to rot. Wait until the plants emerge then water sparingly. Planting time is the time to put in stakes. I have yet to plant a variety that does not need staking. As the plant matures, tie it loosely to the stake and continue to add ties as the plant grows. I use vinyl ribbon. When the dahlia reaches the height of 18-20 inches, cut the center shoot above the third set of leaves. This creates a plant that is shorter, sturdier and more compact.
Dahlias come in an endless array of colors, shapes and sizes. Browsing the catalogs is nothing short of walking into the candy store and leaving with a sugar high. Be warned: The larger varieties, the ones on steroids, demand attention and good staking. They are heavy-stemmed and prone to topple. The shorter, bushier ones can be every bit as beautiful and far less demanding. Enjoy the drama that the Queen of Fall brings to the garden.
By: Sandy Feather ©2008
Penn State Extension
Q. I planted dahlias for the first time this year. I know they have to be dug up and brought inside for the winter. Can you tell me the best way to store dahlia bulbs over the winter?
A. Although we tend to call all plants that grow from underground structures "bulbs," technically dahlias are tuberous roots. They are not winter hardy in our climate and must be dug up and stored indoors until spring. Dahlias should be dug carefully to avoid wounding those thick, fleshy roots. Cut the majority of the foliage back, but be sure to leave three or four inches of stem attached where they sprout from the tubers. Next year's growth will come from eyes at the base of those stems. If you remove the stems entirely, they will not grow next year.
Brush as much soil off the tuberous roots as possible, but do not wash them. Lay them on an old screen and allow them to dry in a protected, shady area with good air circulation for a week or so. Then store them in a dry peat moss, perlite, vermiculite or sand in shallow trays or cloth bags that allow for air circulation. Keep them in a cool (35 - 50°F), dry place where there is no danger of them freezing.
As I am sure you noticed, the tuberous roots increased in size dramatically over the growing season compared to the small pieces you planted last spring. Avoid the temptation to divide them until next spring. You will have much less trouble with them rotting in storage. You can safely divide them next spring before planting them. Be sure to include a piece of eye-bearing stem with each division. Although they should not be planted outside until all danger of frost has past, you can pot them up earlier and hold them indoors to get a head start on the growing season.