The tropical hibiscus (Hibiscus rosa-sinensis) features evergreen foliage and large, showy flowers that bloom from summer through fall. Although the plant is hardy in U.S. Department of Agriculture plant hardiness zones 10 through 11, it's usually grown as a potted plant since it can't tolerate temperatures below 30 degrees Fahrenheit. Proper care and maintenance keeps a tropical hibiscus healthy and encourages abundant blooms in season.
Soil and Site
Whether you grow hibiscus in the ground or in a pot, the plant needs well-drained but moist soil. Plant outdoor hibiscus in soil high in organic matter and amend the site with a 2-inch layer of compost before planting to help improve it. Soil with a pH near 6.8 provides for the best growth. Use a jungle soil potting mixture or other potting soil formulated for tropical plants in pots. Use a pot that has at least one bottom drainage hole so excess moisture doesn't lead to root rot. Potted plants require repotting into a pot one size larger when the roots fill the old container. Plant hibiscus or place pots in a location that receives all-day sunlight. Outdoor plants can tolerate light afternoon shade in hot climates.
Water and Fertilizer
Evenly moist soil keeps a tropical hibiscus healthy and prevents water stress. Water potted plants when the top half-inch of soil feels dry. Empty the drainage tray beneath the pot after watering; otherwise the soil will absorb the excess and become soggy. Outdoor hibiscus plants usually require 1-to-2 inches of water a week, but they may require more frequent watering during periods of drought. Both potted and garden hibiscus benefit from a soluble fertilizer application once monthly during the spring and summer growing season. Apply a fertilizer formulated for tropical flowering plants, such as a 9-3-13 blend, at the recommended rate on the package.
Bring potted hibiscus indoors if temperatures in your area drop below 50 degrees. Place the pot near a south-facing window that receives all-day sunlight. Some leaf drop after bringing a plant indoors is normal. If the plant drops all its leaves, reduce watering but don't allow the soil to dry out completely. Resume fertilization and normal watering after the plant begins producing a new flush of growth. Both indoor and outdoor plants go semi-dormant in winter, so they only need watering when the soil feels dry. Spreading a 2- to 4-inch layer of mulch around outdoor tropical hibiscus insulates the soil so the plant can better survive brief periods of cold.