Winter Storage for Summer Bulbs and Tubers

groWinter Storage for Summer Bulbs & Tubers

Summer bulbs are the stars of my late summer garden. Dahlias, cannas, glads, acidanthera and eucomis keep the color going long after most perennials have faded. But in the northern half of the country (growing zones 3-7), most of these summer bulbs will not survive the winter outdoors. So when fall comes, you have a choice: treat them as annuals or bring them indoors for the winter.

Overwintering these plants indoors is easier than you may think. Bulbs, corms and tubers are food storage organs, and by the end of the growing season they contain all the energy needed to support another year of growth. Your job is to store them at the right temperature and moisture level until it’s time to replant in spring.

The ideal winter temperature for most of these plants is 45° to 50°F. They also need darkness, high humidity and good ventilation. Good storage places include a root cellar, an unheated bedroom or a cool basement. If you’re sure there’s no chance of freezing, an attic or unheated garage can also work.

cutting

Cut back your dahias either before or after you dig them.

Bringing the Plants Indoors

Start by deciding which plants you want to keep, and label them before the first frost (I use colored survey tape and a black marker). Stop watering and let the foliage either die back naturally or be blackened by the first frost. Don’t rush this process. Shorter days and colder temperatures trigger dormancy and help improve storage success.

If the plants are in containers that are easy enough to move, you can simply bring the containers indoors. Cut off the foliage at ground level and let the bulbs or tubers stay right in the soil. Most will not be watered at all during the winter. Others (details below) will be watered sparingly.

If your plants are not in pots, dig them up soon after the first hard frost. Start by cutting off the stems and leaves just above soil level. Carefully dig up the tubers or bulbs and move them to a warm, well-ventilated place where they will be protected from rain and frost. Letting them cure for a few days will help minimize moisture loss during storage. This is a good time to discard or cut away any plants that were damaged when digging or that show signs of disease.

basement

Plants such as elephant ears, can be overwintered right in the pot. Give them a little light and a very small amount of water. Depending on the humidity level in your storage room, cannas and dahlias can be put into plastic or paper bags. Leave the top open for ventilation.

Storage Tips for Summer Bulbs

Bulbs, tubers and corms may be stored in newspaper, paper bags, peat moss, mesh bags, cardboard boxes or plastic bags. The challenge is to keep your plants from completely drying out, yet also keep them dry enough to discourage decay. Figuring out the best technique requires some trial and error because so much depends on the temperature and humidity conditions in your particular storage area.

Once the plants are stored away, check them monthly, especially if you are still experimenting. Tubers should stay dry, smooth and firm like potatoes. Bulbs and corms should stay firm and feel heavy. If there’s too much moisture, improve the ventilation; if it’s too dry, you can mist with water or tuck in some damp peat moss or growing mix.

When spring returns, divide the tubers, bulbs and corms as needed and replant.

For specific instructions about overwintering dahlias, please click HERE. Below is a quick summary of how to care for some of the others. Click the links for more detailed instructions.

Tuberous Begonias. You can keep these growing as houseplants, or nudge them into dormancy and save the tubers. To do the latter, stop watering and allow the foliage to yellow. Then cut back the stems to 4”. Wait a few more weeks until the stems wither and easily pull away from the tuber. Gently brush most of the soil and store the tubers in dry peat moss at 45 to 60°F.

Caladiums. Dig up the plants before the first frost and lay them out in a warm, dry place for 3 weeks (with leaves still attached). Then remove the dried leaves and store the tubers in barely damp peat moss at 55 to 70°F.

Callas. Let the foliage die back naturally, then dig up the rhizomes and cut back the stems and foliage. Cure the rhizomes in a warm place for several days. Store in dry peat moss at 50-60°F.

Canna. Cut the stalks back to a height of about 6”. Dig around the clump and carefully lift it out of the ground (canna tubers are very brittle). Leave soil attached to help protect tubers. Store root balls in loosely gathered plastic bags at 40 to 50°F.

Elephant Ears. If the plant is growing in a pot, cut off most of the leaves and bring it indoors before the first frost. Provide a small amount of light and water sparingly through the winter. Cool temperatures (55°F) will keep the plant alive, but semi-dormant. If the tuber was planted in the ground, cut the foliage back as above and dig up the tuber. Plant it in a container for the winter and treat as above.

EucomisHymenocallis, Nerine, Crinum. Bring the plants indoors and let the foliage dry naturally until it pulls away easily. Leave bulbs in dry soil or store them in mesh bag at 50°F.

Gladiolus and Acidanthera. Dig up the plants after or just before the first frost. Move them to a dry, well ventilated place for a few weeks until the stems wither. Cut the stems about 1” above the corm. Discard the old corms and trim off roots as needed. Cormels (baby corms) can be rubbed off and discarded. Store the corms in mesh bags at 40 to 50°F.