How to Store Flower Bulbs Over Winter
If you tenderly removed all of your precious summer-flowering bulbs from the garden just after the first frost, you may wonder what on Earth to do with them until spring. Various techniques are available for storing most flower bulbs, roots, corms and rhizomes during winter.
Think of Storage as Bulb Hibernation
You'll get in trouble if you think storing flower bulbs is like storing Christmas ornaments or Grandma's good china. Even though bulbs are dormant during winter, they remain alive, more like bears in hibernation or Sleeping Beauty than inanimate objects. That means the bulbs need to breathe, making air-tight containers a really bad idea for them. You wouldn't put a hibernating bear in a sealed plastic container; don't do it to your bulbs.
Also avoid storing bulbs in an area of high heat, high humidity or freezing temperatures. The location also must protect the bulbs from hungry rodents.
- If you tenderly removed all of your precious summer-flowering bulbs from the garden just after the first frost, you may wonder what on Earth to do with them until spring.
- Even though bulbs are dormant during winter, they remain alive, more like bears in hibernation or Sleeping Beauty than inanimate objects.
Provide Basic Storage
Each gardener has her own best bulb-storing practice, and how you do it depends in part on the type of bulb. The basic method to protect bulbs in winter remains largely the same, however. Follow a simple procedure after the bulbs are out of the ground, cleaned and cured by drying.
Divide clumps of bulbs into smaller clumps or individual bulbs if you prefer smaller groupings. Some plants require division more than others. For example, divide root clumps of canna lilies (Canna x generalis) and dahlia (Dahlia spp.) before storing them.
Label bulbs to avoid confusion later. Label the storage container if all bulbs within it are of the same cultivar. Use a permanent marker to write the species and cultivar directly on large fleshy roots such as the corms of gladiolas (Gladiolus spp.). If you label a clump of roots, write the name of the plant on several individual roots in case the clump breaks into several pieces during winter storage. Alternatively, use wood-and-wire "tree labels," and attach them to the roots.
Place the clean, dry bulbs or other root structures in a paper bag with several tablespoons of a fungicide mixture, also called dusting sulfur or bulb dust, to protect the plants during their dormancy. Follow label directions as to the exact amount of the mixture to use. Shake the paper bag gently but vigorously. Select a mixture specifically labeled for the species of bulb or root.
Wrap individual bulbs in newspapers or small paper bags, and put them in storage boxes, paper bags or mesh bags. Alternatively, store the bulbs in such a way that they do not touch one another by packing them in sphagnum peat moss, vermiculite or perlite in storage boxes, paper bags or mesh bags. If you use storage boxes, then do not stack the bulbs more than three deep. If you store them in mesh bags, hang the bags to let air pass through them.
- Place the clean, dry bulbs or other root structures in a paper bag with several tablespoons of a fungicide mixture, also called dusting sulfur or bulb dust, to protect the plants during their dormancy.
Put the bulbs in a dry area where the temperature will not dip below 32 degrees Fahrenheit during winter. The ideal storage temperature varies among bulb species but generally is 35 to 65 degrees Fahrenheit.
Check on the bulbs periodically throughout the winter. If you see rotting areas or signs of mildew, use a sharp garden knife to scrape the affected areas and dust them again with the fungicide mixture. Sterilize the knife before and after using it by soaking it for five minutes in a solution that contains equal amounts of rubbing alcohol and water; let the knife air-dry.
Each bulb has a certain temperature range in which it can survive winter outdoors. That range is the plant's U.S. Department of Agriculture plant hardiness zones. For example, the USDA zones for canna lilies are 8 through 11; for dahlias they are 8 through 10; and for gladiolas they are 6 through 10.
Some bulbs or root structures must be stored in slightly damp packing material to make it through winter. Check at a garden store if you are uncertain which packing material a bulb or root structure needs.
Teo Spengler is a docent with the San Francisco Botanical Garden and a staff writer with Gardening Know How. She has written hundreds of gardening and plant articles for sites like eHow Gardening, Gardening Know How and Hunker. She holds a JD in law from U.C. Berkeley, an MA in English and an MFA in Creative Writing.