“There was a cool night recently, and I am wondering when I should bring in my tropical plants that are in containers on my deck. One of my favorite plants is a hibiscus.”
— Jeff Blumquis, Plainfield
It is best to move your tropical plants inside when temperatures drop below 50 degrees Fahrenheit. Many will do poorly in cold, rainy weather. Start the process by inspecting the plants for insect pests such as aphids, spider mites and mealy bugs. Spray the leaves with a strong stream of water to knock most insect pest off the foliage. Mealy bugs can be wiped off the leaves with a cotton swab dipped in rubbing alcohol. Clean up the plants by pruning out any yellowing leaves and reducing the plants’ size as needed.
Gradually acclimating the plants to indoor conditions can make for a smoother transition, if you have the time to do so. Start by moving the plants into the shade for a few hours a day and gradually increase the time the plant is in the shade over a period of 7 to 10 days until the plant is in the shade all day.
Rapidly changing weather conditions in the fall may not allow this approach. If there is one cold night, with a long period of warm weather predicted to follow, then you can bring the plants back outside after the cold night to extend the display. The most important thing is to get the plants inside as temperatures drop below 50 degrees Fahrenheit. In fall seasons, when there is a more gradual drop in temperature, you push the limits by leaving the plants out later, with night temperatures dropping into the 40s, as they will have acclimated to colder weather. A light freeze over a couple of nights can kill these plants.
Since you are bringing your hibiscus inside for the winter, I assume that it is a tropical hibiscus growing in a pot. If your hibiscus has glossy, deep green leaves, and large orange, red, yellow, pink, peach, salmon or double flowers, then you likely have a tropical hibiscus. Many tropical hibiscuses have more than one color in a bloom.
Keep your plant in a relatively small pot, as hibiscus flowers best when its roots are crowded. Try giving your plant a rest for a few months when you bring it in by minimizing pruning, reducing watering, and moving to it to a cool room with bright light. Do not push it to flower over winter and save old foliage.
It is likely that some leaves will turn yellow and fall off as the plant adjusts to a new environment inside. Other tropical plants may do the same thing as a response to the dramatic change in environment. In March, cut the stems back, move into a sunny location and increase watering. When new growth appears, start fertilizing lightly every couple of weeks. Five to six hours of full sunlight day is important for these plants to perform well while inside.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at email@example.com. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.