Many bulbs can be saved for next year, allowing home gardeners to preserve their favorite flowering plants through the dormant season. A bulb, in the general gardening sense, is an underground storage structure—including true bulbs, corms, tubers, and rhizomes—that holds the plant’s energy reserves. This structure allows the plant to survive unfavorable periods, such as winter or drought, by entering a state of dormancy. Successfully saving a bulb requires understanding its specific needs for overwintering, which depends entirely on the plant’s natural tolerance for cold temperatures.
Identifying Bulbs That Require Lifting
The decision to lift a bulb for winter storage is based on its classification as either “hardy” or “tender.” Hardy bulbs naturally tolerate cold temperatures and require chilling to initiate spring bloom. These are typically left in the ground in most climates. Classic examples include tulips, daffodils, hyacinths, and crocuses.
Tender bulbs originate from tropical or subtropical regions and cannot survive a hard freeze. They must be manually lifted from the garden before the first deep frost in colder regions. This group includes popular summer-blooming varieties like gladiolus (corms), dahlias (tuberous roots), cannas (rhizomes), and tuberous begonias.
Preparing and Curing Bulbs for Storage
The preparation process begins at the end of the growing season to ensure the bulb has stored maximum energy for the next year. Wait until the foliage naturally begins to yellow and die back, as the leaves are actively transferring carbohydrates to the underground structure. Cutting the foliage too early deprives the bulb of the energy needed for next year’s growth and bloom. Once the foliage is mostly yellowed or blackened by a light frost, gently dig up the bulbs using a fork to minimize the risk of damage.
Cleaning and Inspection
After lifting, the next step is cleaning, which involves removing the bulk of the soil clinging to the bulb. This is often done by carefully brushing off the dirt without damaging the outer skin. If bulbs are lightly washed, they must be completely dried immediately afterward to prevent fungal development. Any damaged, soft, or diseased bulbs should be discarded now to avoid contaminating the healthy stock during storage.
Curing
The final preparation step is curing, an initial drying period that hardens the outer layer of the bulb, corm, or tuber. Curing takes place in a cool, dark, and well-ventilated location, ideally between 60 and 70 degrees Fahrenheit (15 to 21 degrees Celsius). This process seals the bulb’s outer surface, preventing moisture loss and discouraging the growth of rot-causing pathogens. Curing duration varies, lasting from a few days for many tubers up to three weeks for corms like gladiolus.
Maintaining Optimal Storage Conditions
Once the bulbs are fully cured and dry, they require a cool, dark, and consistent environment to complete their dormant period. The ideal temperature range for most tender bulbs is between 40 and 50 degrees Fahrenheit (4 to 10 degrees Celsius). Maintaining a stable temperature is important because fluctuations can encourage premature sprouting or cause the bulb to freeze. Suitable locations include basements, unheated crawl spaces, or root cellars that remain consistently cool and dry.
Storage Medium and Ventilation
To prevent the bulbs from drying out completely or developing mold, they should be stored in a breathable medium. Materials such as dry peat moss, vermiculite, or sawdust work well, offering cushioning and absorbing excess moisture while allowing air circulation. Bulbs should be nested within this material and prevented from touching one another, as direct contact can facilitate the spread of rot or disease. Proper ventilation is paramount, requiring the use of non-airtight containers such as cardboard boxes, mesh bags, or paper bags.
Winter Monitoring
Check the stored bulbs periodically throughout the winter months to monitor for signs of shriveling or mold. Shriveling indicates too little humidity, in which case the storage medium can be lightly misted. Mold suggests too much moisture, and moldy bulbs should be immediately separated and discarded to protect the rest of the stock.