Over-wintering large, flowering tropical plants like Hibiscus rosa-sinensis is always a challenge. They never thrive in the living room the way they do outdoors. Leaves turn yellow and drop, flowers seldom appear. Assorted pests do appear — in droves. No wonder gardeners dream of exiling these shrubs to the basement, where they can be out of sight and out of mind until spring.
This kind of hibiscus never sleeps, however, and trying to store yours as though it were dormant may give you a rude awakening. If you want to try it anyway, keep the plants cool, 45º to 50ºF. Expect them to drop all their leaves. They will likely get bugs. And they will still need to be brought into light well before summer planting time.
A better choice is a room that gets lots of light and is cool enough to slow growth, 60º to 65º. If you must put hibiscus plants in the living room, keep them in the sunniest place, away from direct heat and far enough from the window so they don’t suffer big temperature swings from night to day. There is no point in misting, but if you don’t have a humidifier this would be a good excuse to get one. Keep the soil barely but consistently moist, and don’t feed unless flowers appear. Watch out for aphids, whiteflies, and red spider mites. If you see them, treat promptly with insecticidal soap.
Hibiscus is tough. The plants will not be glorious inside, but they will survive. Cut them back in late April, removing leggy branches and working to create a pleasing shape. New growth should start almost at once. It is tempting to set the plants out as soon as the danger of frost is past, but hibiscus is a heat lover that will be happier inside until it is warm out day and night — late May or early June.
Alternatively, treat hibiscus as an annual indulgence. While they are still beautiful, give your plants to somebody with big windows and no qualms about getting rid of ailing ornamentals. Enjoy a carefree winter, and get new ones next year.