The dormancy of a hibiscus in winter depends entirely on the specific variety of the plant. Hibiscus plants are popular for their showy, vibrant flowers, but their winter survival strategy is not uniform across the genus. Confusion often arises because two completely different types of hibiscus are commonly grown in gardens, each requiring a distinct approach to cold weather. Understanding which type you have is the first step in ensuring your plant successfully survives the colder months.
Identifying Your Hibiscus Type
The distinction between the two major types of garden hibiscus centers on their tolerance for cold temperatures: Hardy Hibiscus and Tropical Hibiscus. Hardy Hibiscus, which includes species like Hibiscus moscheutos (Rose Mallow) and Hibiscus syriacus (Rose of Sharon), are true perennials that naturally enter a period of dormancy. These varieties are suitable for colder climates, typically USDA Hardiness Zones 4 through 8, and withstand temperatures well below freezing.
Tropical Hibiscus (Hibiscus rosa-sinensis) is an evergreen shrub that cannot tolerate frost. This type thrives in warm, frost-free environments (USDA Zones 9 through 11) and will die if exposed to prolonged temperatures below 32°F (0°C). Hardy varieties typically die back to the ground each winter, while tropical types are continuous shrubs with glossy leaves. If your hibiscus dies completely down to the ground, it is likely a hardy type; if it is a continuous, woody plant that must be moved indoors, it is tropical.
Winter Care for Hardy Hibiscus
Hardy Hibiscus undergoes a true dormancy, which is necessary for its long-term health and survival in cold regions. As temperatures drop in late fall, the plant loses color, flowers drop, and the entire structure dies back to the soil level. This process is a natural adaptation and should not be mistaken for the plant dying.
Care involves preparing the root crown for insulation against the cold. After the foliage dies back, cut the stems down to about 6 to 8 inches above the soil line. Apply a thick layer of protective mulch, such as pine straw or compost, around the base of the plant to insulate the roots. During this dormant phase, the plant requires significantly less water and may not need supplemental watering. The cold period is required for the plant to successfully exit dormancy, ensuring vigorous new growth when warmer spring temperatures arrive.
Managing Tropical Hibiscus Indoors
Tropical Hibiscus varieties do not go dormant and must be moved indoors before temperatures consistently drop below 50°F (10°C) to prevent cold damage. Before bringing the plant inside, inspect and clean it thoroughly to prevent introducing common pests like spider mites and aphids. Wash the foliage with a strong spray of water to dislodge insects, and treat the plant with horticultural oil if an infestation is visible.
Once indoors, the plant requires ample light, ideally a south-facing window, or supplemental lighting for a minimum of six hours daily. The ideal indoor temperature should remain above 60°F (15°C). Keep the plant away from cold drafts or direct heat sources that can dry out the foliage. Although not truly dormant, the plant’s growth slows considerably, so both watering and fertilization must be reduced. Water only when the top layer of soil feels dry to the touch, and withhold fertilizer completely or switch to a reduced schedule during this period of decreased activity.