Overwintering Tender Bulbs

By: Jennifer LaMontagne – Horticulturist – Bloch’s Farm – Green Lake, WI

Now that winter is nearing, it’s time to think about saving your perennials. While some of your plants will be fine remaining in the ground, there are some bulbs, tubers, rhizomes, roots, and corms that cannot survive the deep freeze of a Wisconsin winter. These are often grouped together and called “tender” bulbs. Caladium, canna, dahlia, elephant’s ear, and tuberous begonias are a few examples. With a little bit of effort, you can save some money and your grandmother’s treasured dahlias by digging up the bulbs to store and replant next spring. 

There are a few steps you can follow in order to provide the best chance of success for your bulbs’ regrowth in the spring. Overall, it’s important to keep the bulbs dry and cool. The first step in the process is to keep an eye out for dried foliage or the first light frost which will cause the leaves to wilt. At this time, trim the plant stems down to about six inches, and then use a shovel or garden fork to carefully dig up the bulbs. Discard any bulbs that have signs of damage or bruising as this can lead to disease and rot.

Gently shake off the soil surrounding the bulbs. Many bulbs can also handle a gentle spray with the hose. Avoid removing any protective layers, and if your bulbs have multiplied, leave them together until spring. Then trim the stems down to about two inches.  

Now your bulbs are ready to be dried. This stage takes one to three days for most bulbs, but it can take up to three weeks for others such as gladiolus, calla lilies, and elephant’s ears. Mesh trays or screens are helpful to hold the bulbs and to aid in the drying process. A warm, dry, well-ventilated garage or similar space can be used to dry the bulbs and keep them out of direct sunlight.   

The final step is storing your dried bulbs. Place the bulbs in a few inches of bagged compost, vermiculite, sawdust, or shredded paper. Store the bulbs in a cardboard box, mesh bag or burlap sack, and keep them from touching each other to prevent any potential rot from spreading. Label the containers with species and color for easy spring planting. Place the bulbs in a storage area that is cool but frost-free (35 to 45°F) with a relatively low rate of humidity. Check them occasionally throughout the winter months.

In general, these steps work well for many varieties of bulbs. There are exceptions, however, so be sure to learn about your particular perennials. For more information on overwintering tender perennials check out the UW-Extension Master Gardener website or ask one of your local greenhouse staff.

Bloch’s Farm is now closed for the season but feel free to call 920-294-6000 or e-mail jlamontagne@blochsfarm.com with any questions. Visit our website online at www.blochsfarm.com and follow us on Facebook and Instagram.

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