How to overwinter dahlias, cannas, gladiolus and geraniums

How do I overwinter dahlias, cannas and other tender bulbs?

Dig dahlias, cannas, gladiolus and tuberous begonias after the first frost blackens their tops, let them dry, and store them somewhere cool, dark and frost-free: gladiolus corms at 35 to 40 °F, cannas below 50 °F, and begonia and caladium tubers at 50 °F. Bring geraniums in before frost as cuttings or potted plants, or hang them dormant at 45 to 50 °F.

Dahlias

1. Dig them once frost has darkened the plant. Cut the top back to 4 to 5 inches and lift the clump gently with a fork or spade.
2. Remove as much soil as you can without damaging the roots, and keep only healthy plants.
3. Let the roots dry in the air for several hours, then store them in a dry, cool, frost-proof place. If the air is very dry, wrap the clumps in newspaper or pack them in peat moss, vermiculite, dry sawdust or sand so they do not shrivel.

Cannas

1. After frost kills the tops, let them dry for several days, cut the tops back to 3 to 4 inches of stem, and lift the roots with a fork or spade.
2. Turn the clump over and let it dry for a few hours.
3. Store in a cool, moderately dry place that stays below 50 °F, on racks or in mesh bags so air moves around them. Do not let them freeze, and check them several times over the winter, throwing out any that rot.

Gladiolus

1. Dig the corms after frost, so they mature as fully as possible. Cut the top off 1 to 2 inches above the corm and let the corms dry in the sun for 1 or 2 days.
2. Cure them at 80 to 85 °F for 2 to 3 weeks, then break off and discard the old corm at the base of each new one.
3. Store at 35 to 40 °F in low humidity, in paper or cloth bags or mesh sacks with air around them. A cool basement works. Do not let them freeze.

Tuberous begonias and caladiums

1. When the first fall frost injures the tops, lift the plants, cut the stems at the soil line, and leave the ball of roots and soil intact.
2. Let them cure in a dry, cool place for 2 to 3 weeks, then remove the rest of the soil, stalks and roots.
3. Store the tubers at 50 °F in low humidity, packed in dry peat, sand, sawdust or vermiculite.

Geraniums

1. Take 3- to 4-inch tip cuttings well before frost and root them indoors, or pot whole plants, cut them back to about a third of their height and bring them in.
2. Or dig them before frost, shake the soil off the roots, and hang them upside down in a cool, dark, dry place at 45 to 50 °F. Soak the roots in water for 1 to 2 hours once a month.
3. After the spring frost danger, cut them back to about a third of their height and plant them out.

Source: Michael N. Dana, "Winter Storage of Geranium, Canna, Gladiolus, Caladium, and Begonia" (HO-85), Purdue University Cooperative Extension, which also recommends a protective fungicide at several steps. Enter your ZIP above for when your first frost typically comes.

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