These freshly dug dahlia tubers will be stored in a cool, dry place for the winter.
In most parts of the country, non-hardy summer bulbs, such as gladiolas, dahlias, caladiums, and elephant ears, won't survive over the winter. But all is not lost: You can dig up the bulbs, store them over the winter, and replant them next spring. A lot of work? Not really, especially considering the money you'll save.
These bulbs (technically, rhizomes, corms, and tubers as well as bulbs) originate from tropical or subropical climates and will die if left in the ground in regions where the ground freezes. When should you dig them up? Look at the foliage; if the leaves are green they are still working to provide food to replenish the bulb. Once the foliage begins to turn yellow its job is done, indicating that it's time to dig up the bulbs. This usually occurs around the first light frost.
Here's the procedure:
Using a spade or fork, very carefully loosen the soil around the plants and gently lift the bulbs from the ground. Gently brush off excess soil and discard any bulbs that show signs of disease or rot. Leaving the foliage attached, hang or spread out the bulbs is a warm, dry location, out of direct sun, to "cure" for seven to ten days. Once bulbs have cured, trim the foliage down 1/2 inch from the bulb.
Rather than buying new summer bulbs each year, dig up non-hardy bulbs, store them over the winter, and replant next spring.
Some gardeners protect the cured bulbs from disease by dusting them with a fungicide, such as sulfur, although I've never done this and have had continued success over the years. The largest bulbs will perform best next year; you can compost the smaller ones or store them for planting next spring, knowing they may not produce many flowers.
Stored bulbs must remain dry and receive good air circulation. Avoid storing bulbs in sealed, air-tight containers because this can lead to moisture build-up and rot. Most bulbs store best where temperatures remain around 50 degrees F. Cool, dry basements or unheated garages that stay above freezing are often good locations.
There are several ways to store the bulbs. One method is to place the bulbs in a box of peat moss, sand, or sawdust, spreading them out so the bulbs aren't touching each other. Don't stack bulbs deeper than three layers. My father-in-law places his bulbs in plastic mesh onion bags and hangs them in the garage. Label the bulbs by type and flower color before storing. Check stored bulbs occasionally throughout the winter and discard any that show signs of rot.
Here are some specifics for popular summer bulbs:
Cannas add a splash of tropical color to gardens. In USDA zones 6 and colder, dig up the rhizomes in fall so they don't freeze.
Caladium. In all but the warmest regions (USDA zones 10 and 11), dig up caladiums before the first fall frost and allow plants to dry. Cut foliage back to an inch, then pack the bulbs loosely in peat moss. Keep slightly warmer than other stored bulbs — 50 to 60 degrees F.
Canna. You can leave cannas in the ground in USDA zones 7 and warmer. In colder regions, cut plants back to 6 inches tall after the first fall frost kills the foliage. Carefully lift each clump of rhizomes and store them in one of the ways described above. Or, wrap rhizomes in newspapers and place in a box.
Caladiums are tropical plants that must be dug and stored in a warm place over the winter.
Dahlia. Dahlias are only hardy to USDA zone 8; in colder regions you'll need to dig and store the tubers. In autumn, after frost kills the foliage but before the ground freezes, cut the plants back to a few inches in height. Carefully lift clumps, brush off any clinging soil, allow the tubers to cure for a week or so, then put them in a plastic-lined box filled with perlite or peat moss, spacing them so that none are touching. Store boxes in a dry area at 45 to 55 degrees F. Dahlia tubers mustn't dry out completely; moisten packing material slightly if necessary.
Elephant ear (alocasia and colocasia). These plants must be dug and stored or brought indoors in regions colder than USDA zone 9. Bring container-grown plants indoors and treat them as houseplants. Or, lift tubers, cure, and store in peat moss in a cool, dry place.
Gladiolas. In zones 7 and 8, mulch beds with a layer of hay or straw for winter protection. In colder regions, dig corms before the first frost. Remove excess soil, cut the stalks to within an inch of the corms, and let them cure for 1 to 2 weeks in a warm, airy location. Then remove and discard the oldest bottom corms and store the large, new corms in plastic mesh bags in a well-ventilated, 35- to 45-degree F. room.
Tuberous begonia. Since the tubers are only hardy to USDA zone 9, in colder regions dig them before a frost and let the tubers dry. Store them in a cool (35 to 45 degrees F.) location in dry peat moss.