Last updated: November 5, 2026. Timing depends on your climate and this year’s weather, so treat your local cooperative extension office as the final word for your zone. This guide is based on published advice from several university extension programs and is not affiliated with any of them. Product and material names are examples, not endorsements.
If your dahlias have been knocked down by frost, the clock is ticking on next year’s flowers. In most cold-winter climates, dahlia tubers will not survive the ground freezing, so the short answer is: cut the stalks, dig the clumps, let them dry, and keep them cool, dark and barely moist until spring. The details below show where university extension sources agree, where they differ, and how to pick a method that fits your space.
Quick answer: the 6-step routine
- Wait for a killing frost (or your local date if frost is late), then cut the stalks down.
- Let the clump rest in the ground for about a week so the tubers firm up.
- Dig carefully a foot or so away from the stalk so you do not cut the necks.
- Rinse gently and dry out of the sun in a cool, dry place.
- Pack in a dry or barely damp medium such as wood shavings, peat moss or vermiculite.
- Store at roughly 40–50°F (4–10°C) and check them about once a month.
Do you need to dig dahlias at all?
It depends on your winter. Washington State University Extension says gardeners in zones 8–10, where winter temperatures rarely drop below 20°F, can cut the plants to the ground and leave the tubers in place. In zone 7 it may work if the winter is mild and water does not funnel into the tubers and cause rot, and WSU describes dig-and-store for zones 3–6. Cornell Cooperative Extension (Monroe County) is blunter for colder areas: zone 6 is not mild enough to leave tubers in the ground over winter. The tubers are thin-skinned and are destroyed if a freeze reaches about 6 inches deep, according to WSU.
Not sure of your zone? Check the USDA Plant Hardiness Zone Map, then compare it with your local extension office’s advice, since microclimates and wet soil change the odds.
When to dig: frost timing
Extension sources give slightly different timing, and the differences are small enough to work around:
- Iowa State University Extension: cut plants back to 2–4 inches above the ground within three or four days of a killing frost, then leave them in the ground another six or seven days to “cure.”
- Cornell Cooperative Extension: cut the stalks to 2–3 inches and allow one to two weeks for the tubers to harden. If there has been no killing frost by the first week of November, dig then.
- WSU Extension: after a hard frost or by mid-November, whichever comes first, cut the stalks to about 6 inches and wait at least a week before digging, which helps the eyes develop and makes dividing easier.
The practical takeaway: after the frost, cut the stalks, wait roughly a week, and dig on a dry day. If you have not had a frost by mid-November, do not wait forever.
How to dig without damaging the tubers
Use a garden fork or spade and start well away from the stalk. Cornell suggests digging in a circle 12–18 inches across, and WSU says to dig down on all four sides about a foot out before lifting. The reason is simple: a tuber with a broken neck will not grow. Cornell also recommends keeping a label with every clump, because tags can get lost in washing, so write the variety on a durable tag or directly on the tuber with a permanent marker.
Washing and drying
Shake off loose soil and rinse the clump gently with a hose on a low setting. Iowa State recommends washing, then drying for 24 hours. Cornell allows more time, saying drying can take two to five days depending on conditions, and that cut surfaces need 24–48 hours to heal. WSU says to dry clumps overnight in a cool, dry place out of the sun. Because the range is wide, a sensible rule is to dry them until the surface feels dry to the touch, not leathery. Cornell’s key point: making sure the tubers are completely dry matters more than any treatment you add afterward.
Do not leave tubers outdoors on concrete or in freezing temperatures to dry. Cornell warns that concrete can chill them fatally and that overnight temperatures below 35°F can kill them.
Trim, divide or leave the clump whole?
Sources disagree, and either approach can work:
- Store the clump whole (Iowa State does not mention dividing): simpler, fewer cuts, but it takes more space.
- Divide into smaller clumps in fall, split to single tubers in spring (Cornell): easier to store, and you can see the eyes more clearly later.
- Divide before storage, keeping an eye on each piece (WSU): cut each tuber away from the main stalk with at least one eye, and discard any tuber without an eye.
Whichever you choose, trim off thin feeder roots, and cut off very thin-necked tubers, which Cornell says will not grow next year. The large old “mother” tuber will not produce a plant again either.
What to pack them in
| Medium | What sources say |
|---|---|
| Wood shavings or sawdust | Listed by Iowa State, Cornell and WSU (pet bedding shavings are one option) |
| Peat moss | Listed by Iowa State, Cornell and WSU |
| Vermiculite | Listed by Iowa State and Cornell |
| Potting soil | Cornell lists it; WSU says not to use it, so skip it if you can |
For containers, Iowa State suggests cardboard boxes with clumps placed upside down and covered with the medium. WSU suggests a cardboard box or a container lined with 10–12 sheets of newspaper, or mesh net bags. Cornell lists plastic bags, plastic boxes or foam produce boxes, placed in a box or tub to keep out light. Whatever you choose, keep the material only slightly damp and give the tubers a little airflow.
The right place and temperature
Aim for a cool, dry, dark spot that does not freeze: an unheated basement, an insulated garage corner, or a closet against an interior wall. Iowa State and Cornell give 40–50°F as the target (Cornell calls about 45°F ideal, with a range of 35–50°F), while WSU allows 40–60°F and warns that tubers shrivel if too warm and rot if too cold. Keep the containers off bare concrete floors.
Monthly checks: rot, mold and shriveling
Cornell and WSU both recommend checking about once a month. Cornell says to watch for mold, rot and shriveling, and describes the ideal as moist but not too moist, dry but not too dry:
- Rotted or mushy tubers: remove them right away so they do not spread problems.
- Shriveled tubers: lightly mist them with water or lightly moisten the medium (WSU and Cornell both suggest this).
- Moldy tubers: improve ventilation and dry them out; if rot is spreading, discard the affected pieces.
Spring: waking them up
Cornell suggests bringing the tubers out of the dark in late February, opening the containers at room temperature and keeping them in light so the eyes begin to swell. Plant outside after your last frost date once the soil has warmed, and divide to single tubers with at least one eye each if you did not already.
Common mistakes to avoid
- Storing tubers while still wet, the most common cause of rot.
- Breaking the neck while digging or washing.
- Letting them freeze or sit on cold concrete.
- Skipping labels, then forgetting which variety is which.
- Storing in sealed plastic with no airflow.
Keep your fall garden on track
While you are cleaning up the dahlia bed, you may be planning other fall jobs. Our guide to planting tulip bulbs in fall covers timing and depth for spring color, and the cut back perennials or leave them guide helps you decide what else to trim now. For the full seasonal to-do list, see the fall planting calendar, and if you are putting in garlic this month, read how to plant garlic in fall.
FAQ
Can I leave dahlia tubers in the ground over winter?
Only in mild climates. WSU says zones 8–10 can leave them in the ground, zone 7 may work in a mild winter with good drainage, and colder zones should dig and store.
How long should dahlia tubers dry before storage?
Extension sources range from overnight to five days. Dry them until the surface is dry to the touch, and let cut surfaces heal for at least 24 hours.
What temperature is best for storing dahlia tubers?
Most sources point to 40–50°F, with Cornell calling about 45°F ideal. Avoid freezing and avoid warm rooms.
How often should I check stored dahlia tubers?
About once a month. Remove anything rotten and lightly moisten tubers that look shriveled.
Sources
- Iowa State University Extension and Outreach, Yard and Garden: “How do I over-winter dahlias?” (updated December 2024).
- Cornell Cooperative Extension, Monroe County: “Fall Dahlia Tips” (September 2020).
- Washington State University Extension: “Overwintering Dahlias” (Kathy Wolfe, 2018).
- USDA Agricultural Research Service: Plant Hardiness Zone Map.
