Chinese hibiscus is a tropical plant that produces large single or double blooms. The flowers of double hibiscus have two layers of petals, giving them the pleated look of rose blossoms. This feature occurs when the plant’s genetic makeup causes its male organs to develop into petals instead of stamens. Some plants end up with no male organs at all and are sterile, unable to make any pollen. Caring for a double hibiscus plant is similar to caring for a single tropical hibiscus.
Grow double hibiscus in fast-draining soil with a pH between 5.5 and 6.5. Find out your soil’s pH with a test kit from a garden supply shop or by submitting a soil sample to your local cooperative extension office.
Separate multiple hibiscus plants by 5 feet or grow them 4 feet apart if you’re forming a hedge. Plant them in pots if the temperature drops below 50 degrees Fahrenheit where you live. Take the double hibiscus indoors whenever it gets that cold.
Irrigate your double hibiscus to a depth of 18 inches once a week. Apply all the water at once instead of dividing it into short irrigation sessions through the week. Make a 3-inch-deep mulch ring around the base of the plant to slow evaporation. Keep the mulch material from touching the base of the plant. Use pine bark, pine needles or oak leaves.
Feed your outdoor double hibiscus an all-purpose fertilizer once a month. Increase frequency to every two weeks if you have a potted plant. Read the manufacturer’s instructions of the brand you select for application rates.
Trim double hibiscus to remove dead, broken and diseased branches any time you notice one of these problems. Prune one-third from mature plants in early spring to promote new growth.