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Storing Tender Bulbs

University of Minnesota Extension, Stearns County News
October 1, 2014        
Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns & Benton Counties


Storing Tender Bulbs
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (10/01/14) — The temperatures have begun to dip, the leaves have turned colors, and the number of days before the ground begins to freeze are numbered.  Soon it will be time to dig up your tender bulbs such as dahlias, gladiolus, caladiums, canna and calla lilies and store them indoors for winter.  If not dug up and stored in the proper manner, these plants’ tender bulbs will not survive the cold Minnesota winter.  A tender bulb refers to plants that have a fleshy storage structure such as a bulb, corm, tuber, or root.

The general rule of thumb is to dig your tender bulbs out of your gardens after the foliage begins to dry up or is killed by frost. Once the timing is right:

  • Carefully dig up the tender bulbs. Use a fork or spade to gently loosen the roots several inches away from the plant’s base. Typically 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 is done, it makes the structure more susceptible to disease or rot.
  • Clean the tender bulb. Most plants need a gentle wash, however gladiolus corms store best if left unwashed and simply let dry out and dust off any soil before putting in storage. Old gladiolus corms and cormlets should be removed at this time.
  • Curing the tender bulbs. Curing time varies depending on species.
    • Dahlias, cannas, callas, and caladiums have a short curing period of only one to three days. Dahlias curing should actually occur in an area with high humidity to ensure desiccation doesn’t occur.  All tender bulbs should be stored out of direct sunlight and in well-ventilated areas.
    • Gladiolus, oxalis, freesia, longer curing periods of approximately three weeks is needed for gladiolus, oxalis, and tigridia. Gladiolus should cure in temperatures of approximately 60° to 70°F.
  • Inspect for Pests. Before storing away, thoroughly inspect the materials for any signs of insects or disease. Lightly dust with an insecticide-fungicide according to the product’s label.
  • Label and store tender bulbs.
    • Small sized material such as gladiolus corms can be placed in small paper bags and individually labeled of its content. 
    • Larger material such as dahlias or cannas can either be written on directly with a permanent marker or tagged with a wood-and-wire label.
    • The tender bulbs can then be packed into sphagnum peat or vermiculite. Storage temperatures also vary.
      • Freesia, gladioulus, oxalis, and tigridia should be stored at 35° to 40° F
      • Cannas, dahlias, and glory lily should be stored at 40° to 50° F
      • Tuberous begonia, caladium, and calla lily should be stored at 50° to 55° F
  • Periodically inspect. Check the tender bulbs throughout the winter to ensure there are no signs of rot. Remove any material that shows signs before the entire stock are lost.

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       



Photo credit: University of Idaho Extension


Beth Berlin
Extension Educator, Horticulture
(320) 255-6169
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