Tender bulbs must be dug and stored in a warmer area through Minnesota winters. Most tender bulbs should be dug after the foliage dries up or is killed by frost. If left in the ground over winter, the bulbs will turn to mush.

Dahlias, cannas, and calla lilies need to be dug carefully. Loosen the roots gently with a fork or spade. Dig several inches back from the base of the plants to avoid damage to the roots. Loosen the soil on all sides before lifting the clump of roots and soil. Avoid cutting, breaking, or skinning the fleshy structure because diseases can enter through bruises and cuts, and this can lead to rotting during storage.

Dahlias, cannas and calla lilies can have the soil washed off of them after they have been dug. It works well to place an old window screen across and empty garbage pail, put a clump of bulbs on the screen, and gently remove soil with water running from a garden hose. Gladiolus corms are best left unwashed and allowed to dry. The soil can be removed after the corms are dried.

Dahlias, cannas, callas and caladiums should be allowed to cure for a short time, usually 1-3 days. It is best done away from direct sunlight or drying winds. A garage or garden shed works well. The temperature should be between 60 and 70 degrees and there should be good ventilation.

Gladiolus and oxalis have a longer curing period. They need approximately 3 weeks. After this time, the old corm can be removed and discarded. Gladiolus develop a new corm and babies (cormels) every year.

Before storing gladiolus corms, inspect for insects or disease. Dust with an insecticide-fungicide mixture labeled for the specific plant. Soaking the new gladiolus corms for 6 hours in a mixture of 4 teaspoons Lysol (or other disinfectant) to 1 gallon of water to kill any thrips that may be hiding. Allow the corms to dry before storing. Then an additional step can be taken before storage by dusting with an insecticide powder labeled for gladiolus.

Recommended storage conditions for various bulbs and corms are:

Tuberous Begonia, Caladium and Calla lily – store between 50 and 55 degrees F. in sphagnum peat or vermiculite. Dig after frost has killed the foliage. Use plastic bags filled with dry peat moss, vermiculite or perlite for calla lilies and leave the top of the bag open or punch holes in it for air exchange. The rhizomes will shrivel if they dry during storage. Tuberous Begonias are difficult to store. These tubers like moist conditions with good ventilation to avoid mold. Store in a slight moist medium.

Cannas -Dig rhizomes in the fall after the frost has blackened the foliage. Cut the stems back to 2-3 inches, dig and let them dry. Store between 40 and 50 degrees F. in box of sphagnum peat, vermiculite, or sand.

Dahlias – Dig tubers after frost has killed the foliage and the stems are cut back to 2 to 3 inches. Cure in high humidity to avoid drying out. Pack roots in slightly moist vermiculite or sphagnum peat. Roots can be put in plastic bags with small perforations or boxes and covered with vermiculite or peat. Store between 40 and 50 degrees F.

Freesia and Gladiolus – Store between 35 and 40 degrees F in shallow trays, mesh bags, old nylon stockings or labeled paper bags.

Remember to check stored bulbs periodically during the winter. Remove any damaged or rotting material. With tuberous roots like dahlias, cut off any rot until you reach clean, white, fleshy tissue. My biggest challenge is finding areas that are cool enough for storage and providing adequate ventilation.