Tender bulbs, corms and tubers such as dahlias, cannas, gladiolus, tuberous begonias, caladiums and elephant ears will not survive a hard freeze in the ground in cold climates. Digging them up, curing them and storing them correctly lets you replant the same plants every year. This bulb overwintering scheduler uses your average first fall frost and last spring frost to give you dates for lifting, storing, starting indoors and planting out.
How to use the bulb overwintering scheduler
- Choose the type of bulb or tuber you grow.
- Enter your average first fall frost and last spring frost. Find them with the frost dates by ZIP code tool.
- Press the button to see lift, cure, store and replant dates, plus storage tips.
How overwintering works
Lifting
Most tender bulbs are dug after the first frost blackens the leaves, which signals the plant to send energy into the storage organ. Use a garden fork a foot from the stem to avoid slicing tubers. Gladiolus corms are different: lift them about six weeks after flowering, before a hard freeze.
Curing
Curing dries the outer skin so the bulb resists rot. Brush off loose soil, do not wash unless you will dry them fully, and let them sit in a sheltered, airy place for a few days to two weeks depending on the plant.
Storing
Pack bulbs in breathable material such as peat moss, vermiculite, sawdust or paper bags, in a cool, dark, frost-free spot like a basement or insulated garage. Aim for around 40 to 55 degrees F depending on the plant, with low humidity. Check them monthly and remove any that rot so it does not spread.
Replanting
Plant out after the last frost when the soil has warmed. Starting tubers indoors in pots four to eight weeks early gives a head start for dahlias, cannas and begonias. Harden plants off for a week before moving them outside.
Which tender bulbs can stay in the ground?
In mild climates (about zones 8 to 10 for dahlias and zones 7 to 10 for cannas) many tender bulbs survive winter outdoors under a thick mulch. Use the growing zone finder to check your zone. If you are not sure, lift a few and leave a few, and compare results the next spring.
Frequently asked questions
Do dahlias need to be dug up every year?
In cold climates, yes. In zone 8 and warmer, they can often stay in the ground with deep mulch and good drainage.
Why did my stored tubers shrivel or rot?
Shriveling means storage was too dry or too warm, while rot means it was too damp or lacked airflow. Adjust moisture and check them monthly.
Can I store bulbs in the refrigerator?
Hardy bulbs such as tulips benefit from chilling, but tender tubers can be damaged below about 40 degrees F. See the spring bulb calculator for hardy bulbs.
These dates are estimates from your frost dates. Adjust to your real weather.