If you have tender bulbs such as dahlias, gladiolus, caladiums, canna and calla lilies, you need to begin thinking about digging them up and storing them for the winter.

The general rule of thumb is to dig tender bulbs out of the garden after the foliage begins to dry, or when killed by frost.

Tender “bulbs” are plants that develop and grow from fleshy storage structures (bulbs, corms, rhizomes, tubers and roots) and will not survive our cold winters outside. You must dig and store them in a proper manner if you want them to grow and bloom again next year.

Here's how:

DIG: Use a fork or spade gently to loosen the roots several inches away from the plant’s base. It works best to loosen the soil on all sides of the plant before attempting to lift up the clump. It is important to avoid cutting, breaking, or “skinning” the fleshy material. If damage occurs, it makes the bulb more susceptible to disease or rot.

CLEAN: Most plants need a gentle wash; however, gladiolus corms store best if left unwashed. Simply let them dry out and dust off any soil before putting them in storage. Remove old gladiolus corms and cormlets at this time.

DRY: Most bulbs need a period of curing (drying) before being placed into storage. Dahlias, cannas, callas and caladiums have a short curing period of only one to three days.

Cure dahlias in an area with high humidity to ensure dehydration does not occur. Cure tender bulbs out of direct sunlight and in well-ventilated areas.

Many bulbs require longer curing periods. Gladiolus, oxalis and tigridia need approximately three weeks to cure.

Cure gladiolus in temperatures of approximately 60 to 70 degrees. Before storing, thoroughly inspect bulbs for any signs of insects or disease. Lightly dust with an insecticide-fungicide according to the product’s label.

LABEL: Place small-sized bulbs such as gladiolus corms in paper lunch bags. Label each bag with the bulb type and cultivar. Write directly on larger bulbs with a permanent marker or tag them with a wood-and-wire label.

STORE: Pack the bulbs in sphagnum peat or vermiculite. Storage temperatures can vary.

  • Freesia, gladiolas, oxalis and tigridia should be stored at 35 to 40 degrees.
  • Cannas, dahlias and glory lily should be stored at 40 to 50 degrees.
  • Tuberous begonia, caladium and calla lily should be stored at 50 to 55 degrees.

INSPECT: Periodically inspect tender bulbs throughout the winter. Remove any bulbs that show signs of rot, or cut out damaged areas in larger bulbs.

If they have dehydrated (they have shrunk and are wrinkled), moisten the layering medium a little, such as with a spray bottle, and re-pack them. If they are very moist, remove from the packing material and air dry for a few days before repacking in dry material.

PLANT: Stay tuned next spring for information about when and how to plant.

Storing tender bulbs can be a bit of a chore, but a cost-saving effort that will add an array of gorgeous flowers to your gardens.

For more information and specific details, visit wimastergardener.org and search "storing tender bulbs for winter."

Until next time, happy gardening!

Robin Trott is a horticulture educator with University of Minnesota Extension. Contact her at 320-762-3890, or at trot0053@umn.