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Digging dahlias ­-- it’s easy with these tips

By Robin Trott - U of M Extension Educator

Last week’s cold night temperatures put an end to our flower growing season. (I don’t know whether to cry or to cheer!)

Each year has its successes and failures, but this year’s highlight was definitely the dahlias. As a first-time dahlia grower, I was pleasantly surprised by the relative ease of cultivating this gorgeous flower.

Dahlias are indigenous to Central Mexico and thrive in well-drained soil. They range in size from half-inch pompons to the “dinner plate” dahlias that may approach 12 or more inches in diameter.

Flower forms include daisy-like single types to fully double types and come in nearly all flower colors except true blues.

Dahlia tubers need to be dug in the fall and brought inside during our harsh Minnesota winters. Digging should be done about two weeks after a killing frost. Tubers dug too early are still “green” and will not store.

Cut the stalk off to about six inches, gently lift tubers with a spade or pitchfork so as not to break the necks. Wash dirt from the roots and allow to air dry, protected from the elements for about 24 hours.

Store your tubers in a medium such as slightly dampened peat moss, sand or pet bedding material (sawdust/shavings). Never store in sealed plastic bags or plastic containers.

Place tubers in crates or cardboard boxes. Line the containers with 10 to 12 sheets of newspaper. Cover the bottom with your packing medium and layer tubers and medium until the container is full.

Store in a cool, dry area (temp of 40-50 degrees). If the temperature is too warm, they will wrinkle/shrivel; too cold, they will freeze/rot. Check your tubers once a month throughout the winter months.

Plant dahlias in the early summer when the ground temperature reaches approximately 60 degrees (late may, early June, about the same time you plant your vegetable garden.)

Dahlias need a sunny location to thrive. An area that receives at least eight hours of direct sunlight is best. Less sun equals taller plants and fewer blooms.

Lay the tuber horizontally four to six inches deep, about 18 to 24 inches apart, and then cover with soil.

Do not water tubers after planting. Wait to water until after the sprouts have appeared above the ground. Do not mulch dahlia tubers, as it does not allow the soil to warm up or tubers to sprout properly.

For more information about selecting and growing dahlias, visit

Finishing up all our final chores before the snow flies may be a daunting challenge, but I am looking forward to sitting back and selecting the seeds and tubers we will grow next year.

Until next time, happy gardening!