Be sure to check out our archive of Garden Journal articles!
Storing Summer Bulbs
If you planted summer-blooming bulbs
this spring, such as gladiolus, dahlias, and cannas, remember that the bulbs (or corms,
tubers, or rhizomes) are not generally hardy in our Maryland winters. They must be dug up
and stored in the fall and then replanted next spring after the danger of frost has past.
The term bulb is frequently used loosely. It is helpful to understand the difference between true bulbs and their relatives. True bulbs grow from enlarged buds surrounded by modified leaves called scales. Examples of true bulbs include onions, tulips and lilies. True bulbs always have pointed tops and divide naturally each year.
Corms resemble bulbs and it isn’t always easy to tell the difference between them. Gladiolus grow from corms, which are actually solid stems. Like a bulb, a corm has a terminal bud at the top that grows to form the stalk, leaves and flower buds, but unlike a true bulb, each summer a new corm forms on top of the old one. The old corm disappears and the roots at the base of the new corm pull it downward into the hole left by the decayed corm. Small corms, called cormels, grow around the base of the new corm.
Rhizomes are also modified stems. Unlike corms, which grow upwards, they spread horizontally underground or on the surface of the ground. Roots grow from their undersides and sprouts emerge from the uppersides to become stems, leaves and flowers. Rhizomes reproduce from these spreading layers. Cannas and bearded iris are examples of rhizomes.
Dahlias and caladiums grow from tubers that are swollen rhizomes (fat roots) of various shapes. Tubers usually grow just below the surface soil and, like bulbs, store food for the plant. Buds on the tubers grow into the stems, leaves and flowers, and a cluster of roots forms at the base. Tubers multiply by division, and as they divide, the old tuber deteriorates.
Tuberous begonias, ranunculus, cyclamen and certain anemones grow in a slightly different manner, from tuber-corms that are flat disks, shaped somewhat like a top. One or more buds emerge from the top and fibrous roots grow from the bottom. Unlike corms that decay at the end of the growing season, tuber-corms grow larger with age.
Carefully dig up the plants once the foliage has turned yellow. Do not start this process too early in the season, for if the foliage is still green the bulbs are still storing food for next year’s bloom. However, be sure to dig up the bulbs before the first hard freeze.
Storing Tubers and Rhizomes
Dig up the tubers, shake off the soil and dry them for a few days with their tops still on. Hang the entire plant in a ventilated garage to dry slightly so that plant nutrients can return to the roots. Then cut off the top, a foot from the tuber and let them dry further. Finally remove the rest of the foliage.
Leave the clump intact, but check each tuber for rot or insect damage before storing it. Cut off any shrunken or dead sections. Dust them with fungicide to guard against rot. Label plant varieties.
Pack each clump upside down, one layer thick, in a tray, box, or basket that is not airtight and cover them with vermiculite, dry sand or dry peat. Store the container in a room that is no warmer than 45 degrees and inspect the bulbs regularly to see that they are not becoming too dry or are beginning to rot. If the bulbs look shriveled moisten the packing material slightly. Discard any rotting bulbs promptly.
Overwintering Gladiolus
Dig up the corms. The old corm will be withered, but on top will be a brand-new one and probably some little cormels between the two. Leave them all attached and don’t cut off the tops immediately.
Tie the tops together in bunches and label them. Hang the bunches in a warm, dry place until both the tops and roots are thoroughly dry. After they are dry, cut off the tops, leaving about an inch of stem. Remove the old corms and discard them. Dust the new corms with a fungicide to prevent disease and store them in a paper bag in a dark, dry, cool but frost-free space such as a closet.
Be sure to check out our archive of Garden Journal articles!
