Yard and Garden: Over-wintering Bulbs



Perennials such as tuberous begonias, gladioli, cannas and dahlias are an integral part of many home landscapes. They put on excellent displays of color until a killing frost. Unfortunately, they will not survive our harsh winter weather outdoors and must be dug in the fall and stored indoors through the winter months. Cultural and winter storage requirements for several commonly grown tender perennials are provided by ISU Extension horticulturists. To have additional questions answered contact the Hortline at 515-294-3108 or  hortline@iastate.edu.

How do I over-winter my gladiolus bulbs? 

Carefully dig up the plants with a spade in late summer/early fall. Gently shake off the soil from the bulb-like corms. Then cut off the foliage 1 to 2 inches above the corms.  Dry the corms for two to three weeks in a warm, dry, well-ventilated location. When thoroughly dry, remove and discard the old dried up mother corms located at the base of the new corms. Remove the tiny corms (cormels) found around the base of the new corms. Save the small corms for propagation purposes or discard them. Place the corms in mesh bags or old nylon stockings and hang in a cool, dry, well-ventilated location. Storage temperatures should be 35 to 45 degrees Fahrenheit. 

How do I over-winter dahlias? 

Several days after a killing frost, cut the plants back to within 2 to 4 inches of the ground. Carefully dig up the tuberous roots with a spade or shovel. Gently shake off the soil, then cut the stems back to the crown. Wash the tuberous roots to remove any remaining soil. Allow the tuberous roots to dry for about 24 hours. After drying, place the dahlia clumps upside down in boxes or other containers and cover them with vermiculite, peat moss or wood shavings. Store the dahlias in a cool (40 to 50 F), dry location. 

How do I over-winter cannas indoors? 

Cut the plants back to within 4 to 6 inches of the ground a few days after a hard, killing freeze. Then carefully dig up the canna clumps with a spade or garden fork. Leave a small amount of soil around the cannas. Allow them to dry for several hours.  Afterwards, place the cannas in large boxes, wire crates or in mesh bags. Store the cannas in a cool (40 to 50 F), dry location. 

How do I over-winter tuberous begonias? 

Carefully dig up the tuberous begonias within a few days of a killing frost. Leave a small amount of soil around each tuber. Cut off the stems about 1 inch above the tubers. Place the tubers in a cool, dry area to cure for two to three weeks. After curing, shake off the remaining soil, then bury the tubers in a small box containing peat moss, vermiculite or sawdust. Store the tubers in an area with a temperature of 40 to 50 F. Do not allow the tubers to freeze. 

How do I over-winter caladiums? 

Carefully dig up the caladiums when the foliage droops and begins to yellow with the onset of cool fall temperatures or wait until after the first hard frost. Place the plants in a warm, dry location for one to two weeks to cure. Afterwards, cut off the dry foliage and bury the tubers in peat moss or vermiculite. Store the tubers in a cool (60 to 65 F) dry location.