Garden Help Desk: Caring for dahlias through winter | News, Sports, Jobs

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Dahlia tuber clumps wait to go into storage after being dug up from the ground. The necks and roots have been trimmed and the dirt has been brushed off. The tuber varieties have been labeled with a Sharpie.

Courtesy Madeline Ta’ala

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Tubers are placed in a clear plastic bin over a layer of peat moss for winter storage. The tubers are aligned carefully to avoid touching. Another layer of peat moss is then added ,followed by another layer of tubers until the bin is full.

Courtesy Madeline Ta’ala

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Buckets of dahlias are harvested in late summer/early fall to be made into bouquets. There are hundreds of different dahlia varieties.

Courtesy Madeline Ta’ala

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Today we have a special contribution about a popular garden perennial from one of our new Master Gardeners.

Dahlias are one of those beautiful, unique flowers that steal the hearts of most growers. If you haven’t grown this lovely perennial before or are trying them for the first time in our Utah climate, you may not know they require some tender loving care in the fall.

Dahlias aren’t winter hardy along the Wasatch Front, so their tuberous roots need to be dug up and brought indoors for cold storage after the first fall frost.

Digging up tubers

Before cutting back and digging up your tuber, identify the dahlia variety and prepare a label. You can tie your label to your clump of tuberous roots or even write directly on a root with a Sharpie-style marker. Don’t dig up multiple tuber clumps without labeling as it’s impossible to tell the variety once they’re above ground and the foliage has been removed.

There are many methods to digging up tubers, but I like to start by cutting off the stem a few inches above the base of the plant to keep things neat and clean. After cutting the stem, gently work a pitchfork or spading fork in the ground around the outside of the tubers. You can also use the pitchfork as a shovel and go under the tuber to loosen it up. Do not use a shovel, as you might accidentally chop your delicate tuber. Once the soil around the tuber is loose, I’ll use my hands to pull the clump free.

With the tuber clump out of the ground, gently brush off the soil and snip the roots at the ends for easier storage. Trim the stem of the clump to about an inch or so in length to reduce the risk of tuber rot and to make dividing easier. Remove any rotting, shriveled or severely damaged tubers during this time as well.

Tip: It’s best practice to sanitize your snips or garden clippers often to avoid the spread of disease among tubers.

Storing tubers

Dahlia tubers are sensitive to moisture and dryness. Too moist, and the tubers rot. Too dry, and they shrivel up. Storing in clear plastic bins makes it easy to see if moisture is gathering or if the tubers are drying out, but any large, sturdy carton or container will do.

Start by placing a layer of peat moss at the bottom of your storage container. Gently lay your tuber clumps on the peat moss, being careful that the tubers don’t touch one another. Add another layer of peat moss to cover the tubers and repeat until the bin is full. Cover the container. No need to add water or additional moisture to the peat moss. The outside of the bins can be labeled with what varieties are placed inside for easier sorting in the spring.

Store bins in a cool, dry place away from sun exposure and freezing temperatures. I store my bins in the cold storage room in my basement and am careful to watch the temperatures. My smart phone reminds me to check the tubers every few weeks to ensure the bins aren’t too moist or too dry. If stacking bins, it’s a good idea to rotate the bottom bin so the tubers closest to cold concrete don’t freeze.

Dividing tubers

You can divide a clump of tubers when you first dig them up or you can do it in the spring when you’re getting them ready for planting. Every division must have a heathy bud or “eye” and a piece of the old stem in order to grow. I find it much easier to identify the eyes of the tuber in the spring as they start to darken and raise slightly in a fashion similar to sprouts in potatoes.

A large tuber clump can produce several viable tubers that will create their own clone plants and tuber clumps the following year. When dividing, be sure to sterilize your snips.

Remove your clump from storage and look closely toward the neck of the tubers for viable eyes on each individual tuber. Almost every tuber will have them. Cut tubers from your clump in clean cuts from the neck/stem area where possible, keeping a viable eye on each. This can be difficult in the beginning, but as mentioned above, the later in the spring, the easier it is to identify eyes.

Once your tubers have been divided, be sure to label each one to keep varieties organized.

Growing dahlias takes a little extra effort compared to many other flowers, but the reward is worth it when you’re harvesting buckets full of fresh blooms through August and September. If you follow these tips, you’ll be able to store your tubers through the winter and continue expanding your dahlia collection with each passing year.