How well your hibiscus plants handle winter cold depends on their variety. The hardy hibiscus common rose mallow (Hibiscus moscheutos) and althea (Hibiscus syriacus), for instance, survive winters outdoors in U.S. Department of Agriculture plant hardiness zones 5 through 8a and 5 during 9a, respectively. Tropical hibiscus, also called Chinese hibiscus (Hibiscus rosa-sinensis), however, is hardy outdoors annually in only USDA zones 9 through 11. For it, even the uncommon frosty night that occasionally surprises Mediterranean-climate gardeners is too much. Store tropical hibiscus plants indoors through their winter dormancy to appreciate their summer blooms for several years.
Boost hibiscus in pots if you want to overwinter the plants indoors. A hibiscus can live for many years in a 10- to 14-inch-diameter container, as stated by the Tropical Hibiscus site. If you like the idea of inground hibiscus shrubs, then sink potted ones up to the pots’ rims in the soil for the summer. When you are prepared to move the plants indoors in autumn, lift and rinse their containers. Hibiscus planted directly from the ground often succumb to root rot once they are lifted and potted for winter.
Preparing Your Plant
Prepare your hibiscus plants for the move two or three days before the autumn nighttime temperature is forecast to hit 40 degrees Fahrenheit. Using clean, sharp tools, prune the plants back back to within 4 inches of the main stems, disinfecting your tools with rubbing alcohol between cuts to avoid spreading plant diseases. Also remove dead leaves, flowers and other debris in the plants and their containers. Preparing helps remove insects that might move indoors with the plants. Decide on a garden hose’s spray nozzle on its best spray, and bend down the plants until all their surfaces drip water.
Making the Go
Whenever your hibiscus are dry, place them indoors near sunny, south- or west-facing windows. If your house is brief on sunlight, set the plants under timed fluorescent lighting for 16 hours every day. The ideal indoor location comes with a temperature between 55 and 70 F; the cooler it is, the less likely hibiscus plants would be to sponsor insects as winter progresses.
Waiting and Watering
Tropical hibiscus typically drop their leaves following a move indoors. So don’t panic if yours lose leaves. They have simply become dormant for winter. During their dormancy, wait for their potting medium to dry almost completely before putting them in a sink or shower for a long, slow soaking. Let them drain fully before returning them for their regular spots. Misting the plants everyday with a good spray of water compensates the reduced humidity of warm indoor air. Instead, set the hibiscus’ pots on shallow trays of water-covered pebbles, and top off the trays’ water as it evaporates.
Waking Them from Winter
In February or March, remove and remove the top 2 inches of the hibiscus’ growing medium. Boost the impacts of the fresh medium with a dose of slow-release, 19-6-12 indoor plant food. For every single 10-inch bud, sprinkle 1 tablespoon of fertilizer, or the fertilizer tag’s recommended quantity, evenly over the growing medium, and water the medium. Plants in bigger pots require more fertilizer, as the fertilizer label instructions indicate. Cut each division back to a leaf node, wait for glossy, green leaves to emerge and then move your hibiscus plants back outside when nighttime temperatures are always above 55 F. Set them in a shaded location, and move them a little closer to sunlight every day for approximately ten days, or until they acclimate to outside life.