Bulbs and rhizomes produce familiar annual blooms in southeast Minnesota gardens. Some, like these baby iris, are hardy and relatively carefree—whereas other varieties, more tender and less winter-hardy, must be dug up and properly stored until spring. (Photo by Nancy North)
Storing Tender Bulbs
PRESTON & CALEDONIA — The only thing I do not like about Autumn is that some of my favorite flowers reach the end of the bloom cycle. The important thing to remember is that if these are tender bulbs, they need to be put into proper storage. This will ensure that you will be able to enjoy some of your favorite flowers and save some money next spring.
Tender bulbs include tuberous begonia, freesia, dahlias, gladiolus, caladiums, canna, Oxalis and calla lilies, and will need to be stored indoors for winter. If not dug up and stored in the proper manner, they will not survive the cold Minnesota winter. (Editor’s note: Unlike many bulbs, irises, like those pictured above, can typically survive in the ground through the winter—unless you’re planning to divide its rhizome clumps and save for relocating in the spring; in that case, they need to be properly stored similar to bulbs.)
The general rule of thumb is to dig your tender bulbs out of your gardens after the foliage begins to dry up or is killed by frost. Once the timing is right, carefully dig up the tender bulbs. Use a fork or spade to gently loosen the roots several inches away from the plant’s base. Typically, it works best to loosen the soil on all sides of the plant before attempting to lift up the clump. It is important to avoid cutting, breaking, or “skinning” the fleshy material. If damage is done, it makes the structure more susceptible to disease or rot.
After the bulbs have been dug, clean the tender bulbs. Most plants need a gentle wash; however, gladiolus corms store best if left unwashed and simply let dry out. Be sure to dust off any soil before putting in storage.
Cure the bulbs
Curing time varies depending on species. Dahlias, cannas, callas, and caladiums have a short curing period of only one to three days. Gladiolus, oxalis, freesia, require a longer curing period of approximately three weeks. Gladiolus should cure in temperatures of approximately 60°F to 70°F. All tender bulbs should be stored out of direct sunlight and in well-ventilated areas.
Next, be sure to inspect for pests before storing away. Pests include both insects and fungus or other diseases. You may consider lightly dusting with an insecticide or fungicide according to the product’s label to avoid pests over winter. Long winters can make it difficult to remember exactly which bulbs are which come spring. I recommend labeling your bulbs as you put them in their final storage space.
Finally, choose a location that is going to have a consistent temperature appropriate for your bulbs’ storage. Freesia, gladiolus, and oxalis should be stored at 35° to 40° F. Cannas and dahlias should be stored at 40° to 50° F. Tuberous begonia, caladium, and calla lily should be stored at 50° to 55° F.
Throughout the winter you will want to check in on your bulbs to ensure there are no signs of rot. If you notice rot or other similar issues remove any material that shows signs before the entire stock, and all of your work, is lost.
If you have additional questions about storing tender bulbs or other agriculture, horticulture or natural resources related topics, please reach out to your local Extension Educator. Residents in Fillmore and Houston counties can call 507-765-3896 or 507-725-5807.
Katie Drewitz is the Extension Educator – Agriculture Production, Horticulture & Natural Resources, University of Minnesota Extension Fillmore and Houston Counties.