Dahlias may be left in the ground over the winter; however, dahlias are susceptible to rot and/ or freeze. Dahlias are not hardy since they are a tuber (thin-skinned) and not a bulb.

If you wish to move or transplant your dahlias to a new location you may do so in the spring. Dahlias cannot be transplanted in the fall. Once you disturb their roots, you must store them for the winter.

If You Live in a Colder Area - Dig Up and Store

If you are in an area where the freeze reaches a depth of 4-6" or more, then leaving your dahlias in the ground is NOT an option. In many climates, dahlias must be dug and stored (see digging and winter storage information) as tubers cannot freeze. In warmer/mild states, including the Pacific Northwest, you may try leaving the dahlias in the ground over the winter. It is never a guarantee, but many customers find that this is a more successful route compared to digging and storing. Dahlias grown in containers or raised beds must be protected over winter as the tubers are more exposed to the elements (top and sides of the container or bed), leaving a greater chance of freezing. Containers should be moved to a garage or location where they will not freeze. If you are unable to move your containers, then we recommend digging and storing your tubers. Tubers planted in raised beds should be dug and stored over the winter.

If You Live in a Warmer Area - Leave in the Ground and Cover

Customers growing dahlias in hot climates year-round (Florida, Southern California, Hawaii, etc.) should dig, divide, and store their dahlias in a cooler/refrigerator for at least 90 days in the winter. Then plant them back out in the spring. They need a minimum of 3 months of rest between growing seasons. (Storage temperature should be 40-50 degrees). Be sure to check on the tubers at least once a month and follow our storage methods and packing medium guidelines.

Leaving Dahlias in the Ground over winter

If you choose not to dig up your dahlias, please remember that you will be at “Mother Nature’s Mercy”. Considered a “tender perennial,” dahlia tubers are the texture of a potato and are susceptible to freeze and rot. If your ground freezes 4+ inches deep during the winter months, this is not an option for you, as the tubers will freeze. For customers in mild climates that choose to leave them in the ground over the winter, we recommend after a killing frost or any time after November 15th, cutting the stocks down below ground level and covering your dahlia beds with plastic. Then you will want to add layers of material such as straw, leaves, or any type of material that will insulate and protect them from the winter weather, like blankets of warmth. If you do not dig in the fall, but would still like to divide your dahlias, (which we recommend at least every other year).

Divide Your Dahlias in the Spring

If you leave your dahlias in the ground over the winter or for multiple seasons without dividing them, you will need to thin the number of sprouts trying to grow in the spring. We recommend only allowing 1-2 main stalks to grow and pinching off all the other sprouts at ground level. If you do not remove these sprouts, your plant will be very weak as too many sprouts will be competing for sunlight and nutrients to grow.

Digging can start 2 weeks after a killing frost or any time after November 15, whichever comes first. You will know that your plants are ready to be dug if they have turned brown and/or black. Do not dig too early, as your dahlia tubers will be stuck in a “green stage” and will not have hardened off for winter storage and will not store well. Cut the stock to about 6" above ground and gently lift tubers with a spade or pitchfork. Be careful not to break the necks of the tubers where they connect to the stalk. We recommend washing off your tubers as many soils will dry like concrete. Your tubers may be divided at this time or in the spring. Tubers do not need to be dry to begin dividing. Then allow them to air dry, protected from the elements for about 12-24 hours, and follow “winter storage instructions.” Do not leave them out in the sun or on a concrete floor to dry. See the digging video below.

Dividing can be done in the fall or the spring.

Dividing dahlia clumps can be done in the fall or in the spring. Eyes (next year’s sprout) are difficult to see if you are unfamiliar with dividing. We suggest dividing the clump into halves or quarters. Using a dahlia dividing knife, linoleum knife, or sharp knife to cut through the stalk (last year’s growth). The eyes will be located on the center stalk, and each root/tuber must have an eye to grow. Not all tubers will have an eye (sprout for next season) that connects to them. Cut surfaces should be allowed to dry overnight before storing or planting them (if the previous year’s crown dividing in the spring), to allow the cut to heal. Different varieties will produce different tuber sizes and shapes. If you are unable to determine where the eyes are located, we recommend taking a “bird’s eye view” overlooking the clump and just cutting down through the center of the stalk, cutting it into halves or quarters. Each section should easily contain 1 or more viable eyes per section of tuber(s). Please see our website, dahlias.com, for videos on dividing. We recommend that all tools used to divide your dahlia tubers be sterilized between each clump when dividing to prevent cross-contamination. Tubers will cut like potatoes in the fall/winter after being dug up, but eyes/sprouts may be difficult to identify.

If you leave your dahlias in the ground and would like to divide them, you will dig them up in the spring when you see sprouts coming through the ground. If you stored your dahlias in clump form, you may divide them once they begin to sprout before planting. Once you have divided them, let the cuts seal/heal overnight, and then you can replant the next day if the weather is not too cold or the ground is too soggy. Do not let your dahlias sit out for multiple days, as they will begin to dehydrate. If it is too cold to replant, then you will need to store them in peat moss until the ground temperature is about 60 degrees. We recommend that all tools used to divide your dahlia tubers be sterilized between each clump when dividing to prevent cross-contamination.

Dahlia tubers must be stored in a medium to prevent dehydration. Use a storage medium such as slightly dampened peat moss or pet bedding material (sawdust/shavings). All storage mediums must be slightly damp. We recommend and use peat moss on our farm for our storage medium.

Tubers should be stored in crates or cardboard boxes. Line your boxes with 10-12 sheets of newspaper. Start your packing medium (peat moss or shavings) in the bottom and layer tubers and medium until the container is full. Never store your tubers in plastic bags or plastic containers, as they cannot be airtight. Store them in a cool, dry area. The ideal temperature of the storage location should be 40-50 degrees. Ideal humidity in storage is 93- 95%, which is difficult to obtain. If the tubers are kept too warm, they will wrinkle and shrivel (dehydrate) and try to grow (sprouting). If the tubers are too cold, they will freeze and rot.

They must have at least 3 months of rest between growing seasons. Mark your calendar and check on your tubers once a month throughout the winter months, looking for dehydration (shriveling), in which case you will need to mist down your peat moss with a bit of water to keep your tubers from dehydrating further. If you find any rot, please cut it off to prevent it from spreading throughout the box. If your tubers are sprouting due to a warmer storage area, leave the sprouts alone and trim them back to 1 – 2" when you are ready to plant. See the video below.