The tropical hibiscus tree, or ornamental shrub, requires warm temperatures for years of healthy blooming. Not suited to year-round outdoor living north of climate zone 9, the hibiscus tree can be grown in pots that are moved indoors when the temperature drops. Regular fertilization and adequate light assure an abundance of blooms. These conditions should be combined with an ideal temperature of around 60 to 90 ° Fahrenheit (15.5-32 ° Celsius). Although there are hardy hibiscus plants, the largest and most colorful blooms are found on the tropical hibiscus tree.
With the proper care, these beautiful flowing ornamentals provide showy flowers all summer. The bright green foliage and brilliant flowers thrive in rich soil and tropical temperatures. Water the plants when dry, as over watering can cause the roots to rot. Whether planted in the ground or in a pot, be sure the plant has good drainage. For maximum flowering, the plants should be given a low phosphorous fertilizer once a week during the warm months.
Sunlight requirements vary with the temperature. High heat and full sun or cool temperatures and low sun are not ideal conditions. A minimum of two hours of direct sunlight is required for flower production. Deep shade allows the hibiscus tree to grow, but not bloom. When temperatures are mild, the plants can tolerate more sunlight.
The ideal temperature range for a hibiscus tree is 60 to 90 ° F (15.5 to 32 ° C). Temperatures above this range will cause flower buds to drop. During high temperatures, the plants should be watered frequently. A brief period of freezing temperatures will usually kill a tropical hibiscus tree. Long before the temperature drops to freezing, the plant should be brought indoors for the cool months.
Time spent indoors during the winter months is a resting period for the plant. Each hibiscus tree should be grown in a pot, rather than planting in the ground and digging up each fall. This disturbs the roots and can be fatal to the plant. Before bringing it indoors, the plant should be cut back and all dead leaves and flowers should be removed. Once indoors, the plant needs warm temperatures, adequate light and sparing water.
Some varieties of the hibiscus tree never do well after being overwintered indoors. Many newer hybrids and other varieties, though, adapt well to a routine of summer outside and resting in winter indoors. The plant will naturally drop leaves over the winter and then develop new ones in the spring. Those hibiscus that do not do well the following summer can be replaced with new plants. Trying different varieties to find the ones that tolerate indoor winters is often advised.