Nothing says "spring is coming" like the first sight of bulb plants pushing their sprouts up through the ground, sometimes through snow, promising spring flowers on the way. But in many regions of the country, non-hardy summer-flowering bulbs (some of which originate in tropical and subtropical climates) won't survive a cold winter. So it's best to dig up those bulbs, store them safely over the winter and then replant them next spring. Having avoided ultra-frosty conditions, your bulbs can keep delivering on your investment in them, adding cheery color to your springtime landscape.
Here's how to dig up most bulbs for safe winter storage:
According to the National Gardening Association's experts, you'll know when it's time to dig up your non-hardy summer-flowering bulbs when foliage has turned yellow. "If leaves are still green, they are still working to provide food to replenish the bulb," say the National Gardening Association's experts. Once foliage begins to turn yellow, that's a sign that its job is done, and it's ready to be stored. "This often occurs around the time of the first light frost."
Using a spade or gardening fork, carefully loosen the soil around the flowering plant and gently lift the bulb from the ground.
Gently brush off any excess soil from the bulb. Inspect the bulb for any signs of disease or rot. If you do see any diseased spots, it's often best to discard the troubled bulb -- but don't place it in your compost bin. The nature of that disease or mold could infect your healthy compost.
Leave the bulb and its attached foliage out in a warm, dry location -- you may hang it in a basket for good air circulation -- to "cure" the bulb for seven to 10 days, say NGA experts.
Once the bulb has cured, trim the foliage down to 1/2 inch from the bulb.
Stored bulbs must be kept dry and have access to good air circulation. "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," advise NGA experts.
Another method is simply washing the bulbs and spreading them in a shaded place so that they can dry. Once dry, store them away from sunlight in a cool, dry spot.
"If you have only a few bulbs, you can keep them in paper bags hung by strings from the ceiling or wall. Store large numbers of bulbs on trays with screen bottoms. Separate your bulbs by species or variety before storing them," says Stacey McCloskey, editor of the blog Master Gardener Girls. As you go, make sure you label the bulbs you're storing, including their flower color, so that you can more easily replant them by groupings or in arranged patterns in the spring.
Never store bulbs in a sealed container, because any moisture that remains in the bulb or soil will lead to rot, ruining your bulbs. Bulbs fare best at a temperature of 60 to 65 degrees Fahrenheit -- so in a cool, dry basement or an unheated garage that stays above freezing. Don't store your bulbs in a space that dips below the freezing point or gets warmer than 70 degrees, says McCloskey. Never store bulbs more than two or three layers deep, because deep piles of bulbs generate heat and decay. And in addition to avoiding too-cold or too-warm conditions, don't store your bulbs in an area where ethylene gas is produced by fruit, or your bulbs could rot.
Check your bulbs periodically over the course of the winter, discarding any that show signs of rot.
Some bulbs require exceptions to the general rules. "Leave the soil on begonia, caladium, canna, dahlia and ismene bulbs," says McCloskey. "Store these bulbs on a slightly moistened layer of peat moss or sawdust in a cool place."
The NGA suggests the following for some specific types of bulbs:
Cannas: You can leave these bulbs in the ground in USDA zones 7 and warmer. In colder regions, cut these plants down to about 6 inches in height after the first frost kills the foliage. Then carefully lift each clump of rhizomes and store them in a method described earlier. Cannas like to be stored in slightly warmer temperatures of 50 to 60 degrees Fahrenheit.
Caladiums: These tropical plants need to be dug up before the first frost, and then let the plant dry. Cut the foliage back to an inch, and then pack the bulbs loosely in peat moss, storing them in a warmer environment of 50 to 60 degrees Fahrenheit.
Dahlias: In cold regions, after frost kills the foliage but before the ground freezes, cut these plants back to a few inches in height. Carefully lift clumps, brushing off clinging soil, and then allow the tubers to cure for at least a week. Then put them in a plastic-lined box filled with peat moss or perlite, spacing them so that they aren't touching. Store in a dry area at 45 to 55 degrees Fahrenheit. Don't let them dry out completely, though. You may need to add some moisture to these loose-lidded stored bulbs.
Gladioli: In regions colder than zones 7 or 8, dig the corms before the first frost. Remove excess soil, cut the stalks to within an inch of the corms, and let cure for one to two weeks in a warm, airy location. Then, remove and discard the older corms on the bottom. Store the new corms in plastic mesh bags in a 35- to 45-degree Fahrenheit room.
For all bulbs, the advice is the same: Do not divide or separate bulbs before storing them.
Done right, your bulbs will spend the winter in a hospitable environment and will be ready to plant and bloom in the spring.