Overwintering tropical plants

COLUMBIA, Mo.– Many tropical plants thrive in the heat and humidity of a typical Missouri summer and can make great outdoor patio plants. But as temperatures drop in the fall, conditions can quickly become deadly.

The simplest solution to this problem is just to let them freeze and buy new plants in the spring, but that can be expensive, and many gardeners grow attached to their existing plants.

“The end of the growing season does not have to signal the end of tropical patio plants that have brought months of enjoyment,” says University of Missouri Extension horticulturist David Trinklein.

If you have the time and enough well-lit indoor space, you can overwinter some tropical plants indoors. “Plants in this category include hibiscus, bougainvillea, mandevilla and palms,” he said.

Many tropical plants can suffer from chill injury, so you should move them inside for the winter when nighttime temperatures regularly fall below 45 degrees.

Hibiscus

“Hibiscus are fairly content indoors and don’t require a lot of space,” Trinklein said. You should cut them back before bringing them indoors, though this will eliminate flower buds that have developed.

Smaller plants placed in a sunny window should bloom periodically throughout the winter. If a sunny spot isn’t available, you can place hibiscus in a cool location and let them drop their leaves and go dormant. Without leaves, the plant won’t need much water, but don’t let the roots dry out. “A rule of thumb is to keep the root system ‘barely moist,’” Trinklein said.

Bougainvillea

Bougainvillea can take up a lot of space to overwinter. “If the plant was in a hanging basket or small container, it can be cut back and placed in a sunny indoor location in a manner similar to hibiscus,” he said.

Because most bougainvillea patio plants tend to be large containers, the more common approach is to place the plant in a cool—but not freezing—location and let it go dormant for the winter. As with hibiscus, you shouldn’t let the roots dry out, but don’t overwater either.

Mandevilla

“Mandevilla is a very vigorous vine that will need to be severely pruned before being moved indoors,” Trinklein said. If it gets enough sun and growing conditions are good while indoors, it might need additional pruning during winter. You can also let it go dormant in a cool location that does not freeze.

Palms

Palms make appealing indoor houseplants as well as outdoor patio plants. “They adjust quickly to the lower light conditions found in the average home, though some of the older leaves might yellow and drop,” he said.

Tuberous begonias and caladium also can overwinter in the home with some success since both tolerate low-light conditions relatively well. If either of these species is growing in containers, bring them in for winter enjoyment as houseplants.

Leave the pests outdoors

“Regardless of the species, tropical patio plants moved indoors for the winter should be THOROUGHLY inspected for pests,” Trinklein said.

Mites are a very common pest of outdoor plants and can be difficult to detect because of their small size.

“While they may not have been a major problem for the plant during the summer, the warm, dry conditions of the average home encourage populations to build during the winter,” he said. “Watch for leaves that are pale or looked stippled, and inspect with a hand lens.”

If mites are present, you can eliminate them by washing thoroughly with a mild detergent or spraying the plant with a pesticide labeled for indoor use on mites.

“With a bit of care, you can keep your tropical plants as houseguests during the winter and put them back to work the following spring as patio plants,” Trinklein said.

For more information from MU Extension about gardening topics, including publications, websites and events, go to extension.missouri.edu and click on the “Lawn and garden” link.