Overwinter Tender & Tropical Bulbs

elephant's ear close up with yellow and green leaves

There are many tropical plants like elephant ear, caladium, cannas and dahlias that can be overwintered with just a little planning and effort allowing you to grow these wonderful, colorful tropical plants in your Iowa garden year after year while stretching your gardening dollar in the process!

To overwinter tropical plants with geophytes, those that have an underground storage structure like a bulb, corm, rhizome or tuberous root, follow these guidelines:

  1. Allow the first frost to brown the foliage.
  2. Using a fork or spade, carefully dig the fleshy bulb, tuber or corm and cut off the foliage that has died back.
  3. Carefully remove as much of the soil as possible. Some sources recommend washing soil from the bulb, but this step is typically not necessary.
  4. Place bulbs in a box, milk crate, onion sack or empty nursery pot. Be sure to label them so next spring you remember the plant, cultivar, and/or color.
  5. Store in a well-ventilated, cool, dark and dry location for the winter. For most of us this is a basement, but a garage, three-season porch or attic may work as well.
    1. Temperatures should not get below 40°F or above 50°F.
    2. Darkness is important to prevent new growth from emerging prematurely.
    3. Good air circulation is important as any moisture that is allowed to sit around these bulbs can lead quickly to rot.
    4. Dry conditions are best but be sure they don’t get too dry. The little bit of soil that sticks to the bulb usually holds just the right amount of moisture to keep things dry but not too dry. Check on the bulbs periodically throughout the winter, if they start shriveling or drying out too much, mist lightly. Many sources recommend storing bulbs in shredded paper, vermiculite or damped peat. In most cases this can create more rot and fungal issues than benefits.
  6. In spring, sort through your box and remove any dried-up or dead pieces. This is the time to divide any tubers or offsets to create more plants or to give to friends.
  7. Pot up bulbs a few weeks to a month before the last frost of the spring. This will give them a head start to go back outside for the summer months.

Prepared by Aaron Steil, Assistant Director | photo caption: elephant’s ear (Colocasia esculenta ‘Mojito’)