By Richard Jauron, Greg Wallace
Part of living in Iowa is dealing with winter and its effects on landscapes. That means taking precautions to ensure that certain plants can survive winter’s harsh blast by overwintering them. Specific steps must be followed to ensure overwintered plants will return to prominence next spring.
Here are some tips from Iowa State University Extension and Outreach horticulturists on how to best overwinter plants. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.
Will cannas survive the winter outdoors in Iowa?
Cannas are perennials. However, they are not winter hardy in Iowa. Cannas must be dug in fall and overwintered indoors. Other tender perennials include tuberous begonia, dahlia, caladium, and gladiolus.
How do I overwinter cannas?
Cut back the plants to within four to six nches of the ground a few days after a hard, killing frost. 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 mesh bags. Store the cannas in a cool (40 to 50 degree Fahrenheit), dry location.
How do I overwinter 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 one 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. Place a layer of peat moss, vermiculite or sawdust in a small cardboard box. Lay the tubers on the storage medium, then cover the tubers with additional peat, vermiculite or sawdust. Store the tubers in an area with a temperature of 40 to 50 degrees Fahrenheit.
How do I overwinter dahlias?
Cut back the plants to within two to four inches of the ground within three or four days of a killing frost. After cutting back the plants, leave the dahlias in the ground for an additional six or seven days to “cure.” Then carefully dig up the dahlias with a spade or shovel. Gently shake off the soil, then cut the stems back to the crown. (The dahlia crown is located at the base of the stem where the tuberous roots are attached.) Carefully wash the dahlia clumps to remove any remaining soil. Allow the dahlias to dry for 24 hours. When dry, place the dahlia clumps upside down in cardboard boxes and cover them with vermiculite, peat moss, or wood shavings. Store the dahlias in a cool (40 to 50 degree Fahrenheit), dry location.
How do I overwinter caladiums?
Carefully dig up the caladiums after the first fall frost. After digging, place the plants in a cool, dry location for one to two weeks to cure. After curing, cut off the dry foliage. Place a layer of peat moss, vermiculite or sawdust in a small cardboard box. Lay the tubers on the storage medium, then cover with additional peat, vermiculite or sawdust. Store the caladiums in a cool (60 to 65 degree Fahrenheit), dry location.
How do I overwinter gladiolus bulbs?
Carefully dig up the plants with a spade in fall. Gently shake off the soil from the bulb-like corms. Then cut off the foliage one to two 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.