Hibiscus Care in California

Overview

• There are about 17 hibiscus species native to North America that occur naturally in wetlands throughout U.S. Department of Agriculture plant hardiness zones 4 through 10, while Asian species of hibiscus are cultivated as ornamentals in USDA zones 8 through 10. In California, the varieties of hibiscus available as nursery plants are generally limited to older hybrids with proven tolerance of varying thermal conditions and other factors found in different elevations throughout the state.

Culture

• Hibiscus enjoys a moist environment with either an inch of rain or manual watering each week. It doesn’t like “wet feet,” however, so well-drained soil enhanced with organic material is necessary. Although full sun is preferred, a site that receives morning sun and afternoon shade is sufficient.

Pruning

• Hibiscus plants reach a height of up to 15 feet within two to three years and the equivalent in spread. Light pruning of wandering growth to shape plants is all that is needed and should be performed in early spring after the danger of frost has passed. Deadheading spent flowers, which initially emerge in mid- to late summer and typically span 6 inches, will encourage a second bloom.

Fertilizing

• The frequency of flowering and length of the bloom season can be increased with the year-round application of fertilizer, although high acid formulas should be avoided due to the risk of bud drop. As a rule of thumb, a fertilizer with a nitrogen, phosphorus and potassium or N-P-K ratio of 4-8-8 is ideal, with an additional monthly application of blood meal. Hibiscus performs best in California gardens that have a soil pH of 5.5 to 6.

Varieties to Consider

• There are several striking varieties of hibiscus that are easier to care for in California than standard tropical species. For example, flower of an hour (Hibiscus trionum), suited to USDA zone 10, is so-named because blooms remain open for only part of the day. In USDA zones 8 through 11, red shield hibiscus (Hibiscus acetosella) features dark burgundy foliage that resembles maple leaves. The cultivar “Turn of the Century” (Hibiscus “Turn of the Century”), suited to USDA zones 5 through 9, has pink flowers with dark edging that lends them the appearance of pinwheels.