Hibiscus plants belong to the Malvaceae family of plants which also includes cotton, okra, hollyhock and desert rosemallow. Hibiscus plants are easy to care for, and there are types that can be grown in most of the country.
There are two types of hibiscus plants: tropical and hardy. Tropical hibiscus cannot be grown outdoors further north than Florida. Hardy hibiscus can be grown as far north as New York. Within these two types are 200 different species.
The hibiscus flower is large, but very delicate with thin petals. Colors can range from pink to plum with two colors of dark, contrasting veins. If the hibiscus has deep green glossy leaves, flowers that are red, pink, orange or yellow, either single or double, and measure from 3 to 6 inches across, it is probably a tropical. If the flowers are salmon, peach, orange or yellow, or double flowered, it is definitely a tropical because hardy hibiscus do not come in these colors or with double blooms. Tropicals can also have bands or spots of a different color. If the plant has dull medium green leaves that are heart shaped and white, pink or red flowers as big as a dinner plate, it is a hardy variety.
Tropical hibiscus plants need to be kept where the temperatures are between 60 and 90 degrees F, whether indoors or out. They can survive in temperatures that are slightly higher or lower for a short time, but they will probably lose leaves, and buds may not develop. If the temperatures drop below 30 degrees F for a few hours, the plant will die. If they are grown further north than zone 9 (Florida), they must be brought in for the winter. Hardy hibiscus can stay out for the winter with very little protection as far north as zone 5--around Washington, D.C. and Pennsylvania. In zone 4, New York, they should be mulched, They will die back to the ground, but will bloom again in the spring.
When planting outdoors, pick a well-drained spot where the roots will not sit in water. If potting for a house plant, do not plant in a container that is more than one size larger than the one it came in. Use a commercial potting soil that is made for hibiscus plants.
During the hot weather, hibiscus needs a good deal of water on a regular basis. Outdoors, make sure the soil is well drained, and indoors, do not let water sit in the saucer. This will cause root rot. Just keep the soil consistently moist. In the cold weather, it is better to let the soil get dry before watering. Then only give enough to moisten the soil. Cold weather plus moisture leads to fungal diseases. Feed hibiscus plants a special hibiscus fertilizer according to the package directions.
Phytophthora is a soil-borne fungus that attacks when the soil dries out in the summer and gets extra wet in the winter. It can be fatal. Collar rot appears as a brown, slimy ring where the root joins the plant. It strikes when the winters are cool and damp and the plant does not have proper drainage. Leaf spot appears as dark brown or black spots on the leaves. It occurs when the plant does not get enough air circulation in wet weather. It can defoliate the plant completely.