Extension Educator, Horticulture
Many gardeners have fallen for the bold and bodacious look of landscape tropicals such as bananas and elephant ears. Their tropical nature, however, translates into winter whimpiness. These plants won't make it through our winters and may even suffer damage at temperatures below 55 degrees F.
So do we let them die a cold death? Of course not! We are gardeners! We hold on to each plant until the last cell succumbs. In addition many of the tropicals get bigger and better in successive years. Here are a few tips to keeping tropicals through the winter.
The winter care of many tropicals such as mandevilla, elephant ears, angel's trumpet (brugmansia) and bananas can be one of two methods: grow as a houseplant or keep dormant in a pot or bare root.
If you have the space, tropicals can be brought indoors and grown as houseplants. Dig the tropical from the garden or bring in the container before day temperatures get below 60 degrees F and before frost. Generally late September into early October works well. Trim plant to a manageable size. Wash plant thoroughly. If you decide to leave plant in original container, drench soil with water to encourage any critters like ants and sowbugs to vacate. If necessary, plant in pot with well-drained potting soil. Place the pot in a sunny location. Do not fertilize during the winter.
As with most houseplants water tropicals about once a week. Most tropicals will not bloom through the winter due to the shorter days unless they receive supplemental lighting. Periodically check for insects such as spider mites. With this method don't be alarmed if many tropicals insist on going dormant and lose their leaves. They often look dreadful during the winter but they will recover once spring arrives.
The other method falls into the "just don't die" category. Many plants have natural adaptations to survive in a dormant state while they wait for better growing conditions. Once tropicals are brought indoors they can be held in dormancy until spring. To keep tropicals as dormant plants leave them in the original pot or place them in a plastic-lined cardboard box. Milk crate style boxes are great for storing tropicals since they stack well for multiple plants. Store pots or crates in a cool dark basement, garage or crawlspace. Anywhere where the temperatures stay about 55-60 degrees is adequate.
Bananas are amazingly tough tropical plants, but they are cold weather wimps. They grow a bit differently then most of our plants. Bananas are not true trees since they never form a woody stem. They are actually the largest herbaceous plant in the world. What appears to be a trunk is really the overlapping leaf bases or petioles of the giant leaves. They grow from a central crown so the leaves can be cut back and some of the side leaf petioles on the trunk can be removed so the plant is a manageable size to bring indoors. Even large ones are fairly easy to dig. I keep mine in the basement in a pot all winter with minimal light and water. Bananas can also be cut down to 10-12 inches and brought indoors to be stored dormant in a plastic bag in a cool dry place.
One banana species, Musa basjoo, is reportedly hardy to zone 4. I haven't tried it myself but I know gardeners who have successfully gotten their hardy banana through the winter by mulching heavily with at least 2 feet of mulch.
Spend a little time now tucking your tropicals in for a long winter's nap.