Bulbs, Overwintering

You can save these special plants

Tender bulbs are a lovely addition to the flower border but many of us are reluctant to invest in them because they cannot stay outside over the winter in our Zone 6 gardens. There are too many spectacular plants in this group to ignore them. Yes, it is a little extra work, but they are worth planting, enjoying and then saving for another year. “Tender bulbs” is a common name given to plants with fleshy underground storage units such as corms, tubers, bulbs and tuberous roots. They are

Considered tender because the underground “bulb” will turn to mush if they are frozen.

Most of these “bulbs” are left outside until the top is hit by a killing frost.  The tops have dies, but the roots are still alive in the warm soil. They are then gently dug up at that time. Dig about a foot away from the base of the stalk, loosening the soil so you keep as many roots as possible. Do not “skim” the skin of the bulb which could cause rotting. Dahlias are the only ones that are cleaned with a hose. Generally, you let the bulb and attached soil dry and then gently knock off excess soil. They don’t have to be clean. They all need to be cured for 1 to 2 weeks, depending on the temperature.

Dry or cure them at 60° to 70° in a well-ventilated room. This will remove excess moisture which could lead to decay. Once dry, remove any foliage. Inspect for insect or diseases. Dust with an insecticide-fungicide mixture labeled for that plant.

Store them in peat moss, vermiculite, sawdust or newspaper at 45° to 50°. All of these “bulbs” do best when stored in a cool, dark and humid place with good ventilation. Fruit cellars and cool basements work well. If your basement is warm, store them along an outside wall. Do not store bulbs in an attic or garage where they may freeze.

Check throughout the winter and discard diseased or insect infested bulbs. Sprinkle with water if they are shriveling. The trick is to keep them just moist enough to not shrivel, but not so moist that they rot.

Bulbs that are grown in a pot are brought inside in the that pot with the original soilless planting mix and placed in the desired storage condition.

Agapanthus – You can 1) Leave the fleshy rhizomes in the container with slightly moist planting medium and store at 35° – 41° or 2) Place the container in a cool greenhouse and water sparingly during the winter. Return to the growing area in the spring.

Tuberous begonias can be kept as a houseplant, or stored dry. To store dry, dig the plant up when the foliage turns yellow and cure with the foliage for 2 or 3 weeks. Gently remove the dried foliage and store at 45° to 60°.

Caladiums – Dig up before the first frost and cure with the leaves attached for 3 weeks. Remove dried leaves and store in peatmoss that is slightly moist at 55° to 70° in the dark.

Canna – After the foliage has been hit by frost and before the ground freezes, cut around the plant about a foot out from the stalk. Lift the clump taking care not to break the tender shoots. Leave the soil that sticks to them. Cut the stalk to 6” and let the clump dry, raised off the ground, for a week. Store the rhizomes in peat moss in a loosely closed plastic bag or cardboard box at 35° to 50°. Check occasionally and mist if dry.

Dig Dahlias after a frost or before the end of October and cut the tops back to 3 inches above the root. Remove loose soil by hand or with a garden hose and discard all damaged or diseased root portions. Place upside down in the sun for several hours to dry. Write the cultivar or color on the tuber with a magic marker. Store dahlia roots at 40° to 55° in a shallow container covered with vermiculite or peat moss. They can be placed in an open plastic bag or closed cardboard box. Sprinkle with water during the winter if the roots begin to shrivel. When dividing in the spring, each division must have a piece of the original stem.

Elephant ears – When the temperatures go into the 40°s bring the plant inside if you want to keep it as a houseplant. Give it a southern exposure and keep moist and warm.  They can also be stored dry in peatmoss at 45° to 50°. In the spring when dividing colocasia tubers, each piece must have a corm in order to produce a shoot. Let the cut up tubers dry a few days before planting them. Some of the newer cultivars of Colocasia do not form large tubers and cannot be stored in a dormant state. They must be overwintered as houseplants.

Gladioli – Dig the plants 6 or 8 weeks after bloom or when the frost hits them.  Cut the leaves no more than one inch from corm. Dry corms in a well ventilated place for 3 weeks at 60° to 70°. Once dried, carefully remove the excess soil and divide the corm. Discard stems, husks, and the older shriveled corm at the base of the cluster. After dividing, cure corms one more week. Dust with Sevin or a bulb dust. Store glads uncovered in a 40° to 50° site.

Gloriosa Lily – Store in the pot or dig the tuberous roots and store like dahlias. They may be stared indoors again after 2 months  of storage.

Zephyranthes (Rain Lilies) – Store bulbs in pot or in peat moss or  vermiculite at 50° to 60°

If you want to get a jump start on the season, these “bulbs” may be planted in a pot with soilless potting mix 8 weeks before the last frost in your area. Do not put these plants outside until the night temperatures average 55°. (first of June)