Here in Eastern Iowa we’ve enjoyed a relatively frost-free October. But when temperatures drop, it’s time to dig up and overwinter tropicals, dahlias, caladiums and tuberous begonias. All of these “bulb-based” plants are actually quite easy to overwinter.
My favorite is the tropical elephant ears (Colocasia). These are foliage plants with huge heart shaped leaves. To overwinter Elephant Ears, dig them up after a killing frost, cutting off the foliage first. Place the bulbs (which can be very large on mature plants) in a warm, dry location for one or two weeks. After drying, place the bulbs in a box with peat moss or wood shavings and store them in an area with a temperature of 70 to 75 degrees.
Cannas are another tropical favorite. Like the Colocasia, wait until a killing frost and cut back the plants to within 4 to 6 inches from the ground. Carefully dig up the canna clumps with a spade or garden fork, leaving a small amount of soil around the cannas. Allow them to dry for several hours and then place them in large boxes, wire crates or in mesh bags and store them in a cool (40 to 50 degrees), dry location.
Tuberous Begonias like the non-stop series, camellia, cascade, carnation, and picotee types can either be brought inside as a houseplant or if left outside, dug up after a killing frost. Dry lifted tubers in a warm location for approximately 2 weeks, then bury tubers in a box or sack filled with sphagnum moss or vermiculite and store in a cool (45 to 50 degrees), dry location.
Dahlias are ready to dig when darkened by frost. Cut them back to within 2 to 4 inches of the ground. Carefully dig up the tuberous roots with a spade, removing as much soil as possible and let air dry. Divide these right after digging since the “eyes” or “buds” are easier to see in the fall. Once dry to the touch, store the tubers upside down in vermiculite in a dry, cool (40 to 50F) location.
Caladiums and Cala Lilies can also be stored for winter. Again after a killing frost, cut back the foliage and lift the Caladium tuber and the Cala Lily rhizome out of the soil, and dry both of them for about two weeks. Then store in vermiculite or peat moss in a cool, dry place.
Periodically check your bulbs, tubers and rhizomes that you are storing over winter for any signs of molding or rotting and discard those right away. In the Spring you can either start these plants early inside in pots or plant directly outside once temperatures warm.
l For questions, call the Linn County Extension Master Gardener Hortline at (319) 447-0647.