Question: This year I planted a variety of tender bulbs including cannas, dahlias and caladiums. Do I really have to dig them up and store them? If so, how and where would I do this?
Answer: The term "tender bulb" refers to those plants that develop from fleshy underground storage structures such as bulbs, corms, rhizomes, tubers and roots that will not survive our winter low temperatures. This includes caladiums, cannas, dahlias, as well as calla lily, elephant ears, gladiolus and tuberous begonias. Some of these bulbs can be expensive and worth the extra effort to dig them up and store over the winter.
Cannas and dahlias are ready to be dug up once the foliage has been blackened by the first frost. The foliage should then be cut back to four to five inches. Allow the roots to completely dry before storing in a cool moderately dry place where temperatures are between 35 and 50 degrees. Cannas can then be planted in the spring as one big clump or cut into divisions that have two to three eyes or buds per section. Dahlias can be divided immediately after digging since their eyes can be seen in the fall. Each division can have at minimum one eye.
When digging up the structures, first loosen the soil directly around the plant being careful not to cut or scratch the fleshy part. Any wound will create an opportunity for disease to enter during storage. Shake off any excess soil and cut off the stems. Remaining soil should be washed off the structures followed by a careful inspection. Any damaged pieces should be discarded.
Before storing all your bulblike structures certain ones require a longer curing process. Most require a curing period of one to three days, but callas should be cured by air-drying at 60 degrees out of sunlight for three weeks. While curing, keep your structures in a dry well-ventilated area with temperatures around 60 to 70 degrees. The tender bulbs should then be stored by layering them with peat moss, sand, newspaper or sawdust in a ventilated container. Adequate space between them is needed to prevent spread of decay if it should occur.
Cannas and dahlias should be stored at 35 to 50 degrees; usually a basement, crawlspace or unheated room provides the appropriate temperatures. Caladiums and tuberous begonias prefer it slightly warmer at 55 to 60 degrees. Storage containers should be rodent proof if placed in an accessible environment.
Periodic checks should be done several times throughout the winter. Besides checking for rotted ones also check the moisture levels. If any wrinkled ones are found the environment is too dry. Moisten the layering material somewhat and repack.
Mona Bawgus is a certified master gardener and consumer horticulturist with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330. Email: