There are several hundred species in the Hibiscus genus but this care sheet focuses on Hibiscus rosa-sinensis, also known as tropical hibiscus, Chinese hibiscus, and Hawaiian hibiscus. Their magnificent blooms may only last a day, but their colors, size and number make up for this all too brief interlude.
Note: there are hundreds of hibiscus cultivars available, each one having slightly different cultural needs. General requirements for many of these plants are described below. Some varieties might be more cold-tolerant, grow larger or smaller, etc. Before buying any plant, be sure to know its individual characteristics and care requirements.
Hibiscus rosa-sinensis are vigorous growers known for their beautiful flowers. Their size ranges from as small as 2 inches in diameter to nearly 10 inches, with most falling somewhere in between. They come in a kaleidoscope of colors and shades. Single or double flowers are available. Most grow as a large shrub and can reach 4-10 feet tall and 3-6 feet wide. This plant, native to Southeast Asia, is the national flower of Malaysia.
These Hibiscus are known for their glossy evergreen foliage and large bold flowers. Plants can be grown in containers and give a tropical feeling on a deck or patio or around a pool. A well maintained plant can serve as a showy specimen while groups of them can act as a screen for privacy. They also make for a great foundation planting in warmer climates.
In general, the more sun this plant gets, the better. Hibiscus rosa-sinensis prefer full sun but will tolerate light shade. The more shade the plant gets, the fewer and likely smaller flowers it will produce. If overwintering, try to place near a southern or western facing window.
Hibiscus require little pruning during the growing season unless space is an issue. Cut back the plant by about half in the early spring to maintain a nice shape and encourage growth. More frequent and lighter pruning may be needed throughout the year for hibiscus that are grown indoors. The plants flower on new wood, so pruning any time during the year won’t stop flowering completely, just delay it.
Hibiscus don’t like to dry out and prefer an evenly moist root ball. After planting in the ground, it is important to give supplemental water the first year as needed until the plant is well established. When potting, choose a container that is sized to the plant. A pot that is too large or too small will make it difficult to keep the plant properly watered. Check your plant daily. Over time, you will get to know it and its water requirements and make adjustments according to how much sun or rain is in the forecast.
It is important to remember that hibiscus are topical plants and require warm temperatures to survive. Many can live in Plant Hardiness Zones 9 to 12. Tropical hibiscus prefer temperatures above 50°F. They will likely show damage and even die at temperatures below 35°F.
When potted, these plants can be overwintered easily by bringing them indoors. Scout for pests and diseases before bringing them inside and treat as needed. Pruning throughout the winter is necessary to keep a compact shape. Giving them an additional hard pruning before they go outside again in the spring is recommended. Hibiscus require less water during the cooler months.
Hibiscus are carefree but do require some fertilizer, especially if grown in containers. Slow release fertilizers are an easy way to keep plants fed throughout the growing season. Liquid fertilizer with a high middle number (phosphorus) applied during the summer can encourage stronger and more blooms. Iron is one nutrient that might need to be supplemented from time to time. Regular feeding is needed from spring through fall but fertilizing can be cut back during winter months. You can completely stop fertilizing when overwintering unless you see nutrient deficiencies.
With the help of beneficial insects and birds, healthy outdoor plants can usually fight off most pest issues. Aphids, thrips, and spider mites are the main ones to look for, with whitefly, scale, and mealybug to a lesser extent. Indoors you will need to be more diligent when scouting and treating for pests and can use a horticultural oil or insecticidal soap to treat most outbreaks. Simply pruning out infected parts works great too!
Hibiscus are known to be susceptible to a few disease issues including powdery or downy mildew and botrytis. Black spots are often seen as well but their causes are vast and hard to identify without proper testing. For proper identification and treatment recommendations, contact your local extension agency.
Hibiscus will occasionally drop unopened buds or their leaves will turn yellow and fall off. Besides pest and disease issues, these problems are often caused by water stress or other factors like significant temperature swings.
Download these scenes from Smithsonian Gardens to use as your desktop background, or on your next Zoom meeting!