Tender bulbs need cool and dry storage in winter

Many of our favorite, sometimes exotic looking summer garden plants like cannas, calla lilies, caladiums and elephant ears grow from “tender bulbs,” which means they need special care in the fall and winter. They will not survive the cold and if left outdoors, will freeze and turn to mush by spring.

Tender bulbs are really not true bulbs, like a tulip or daffodil, which can withstand low temperatures. They are instead plants that grow from fleshy storage structures such as dahlia tubers, rhizomes of cannas and gladiola corms. Many of these plants are expensive, yet easy to keep so it is worth the effort to dig them up and store them in a dry cool place until spring. In some cases, you will be happy to find they have multiplied since you planted them so you’ll have a good return on your investment.



As temperature drops in the fall, the growth of the tender bulb slows. Most recommend removing from the soil after frost but before heavy freeze because you do not want the stem of the bulb to turn soft, which would encourage rotting of the bulb in storage. Take care not to slice into the bulbs. A digging fork is less likely than a shovel to damage them. Excess soil should be shaken off and the stems cut off. You can hose them off but this increases the time to dry them before storing. Give the bulbs a few days under cover in a shaded area or dark garage to dry and to callous over the cut stems.



The two important requirements for storing tender bulbs are to keep them cool (between 35 and 45 degrees) and dry, relative humidity about 50 percent. To store tubers and rhizomes, loosely layer the bulbs between several inches of dry peat moss in a cardboard box. You can line the box with a plastic bag but do not seal that bag tightly when closing the box. Too much moisture will rot the bulbs. Too dry and they will shrivel up.

Basements are often an ideal place but finished basements are likely too warm. If that is the case, put the stored bulbs near an outside wall away from heat sources. If your garage or crawl space stays above freezing, that may work, but in that case, store in a rodent-proof container.

With the wide variety of tender bulbs, it’s best to do a bit of research on storage recommendations for your specific types. It can be as easy as hanging gladiolas in a mesh onion bag. Or it can be the dahlia growers’ precise secrets on preserving their prize winning tubers.

For more information, http://go.osu.edu/storebulbs.

Karsnak is an Ohio State University Mahoning County Extension Master Gardener volunteer.


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