During the cold winter months, warm-weather plants, such as the tropical hibiscus (Hibiscus rosa-sinensis), require protection from frost. Hibiscus plants grow in U.S. Department of Agriculture plant hardiness zones 9 through 10, and are known for their glossy foliage and brightly colored flowers. There are reports of hibiscus plants reaching 15 feet in height, however, most only grow to a height of 5 to 6 feet. Once temperatures drop to 20 degrees Fahrenheit, you'll need to cover the hibiscus plants with a frost cloth.
Distribute a 3-inch-deep layer of leaf mulch around the base of your tropical hibiscus plants. The mulch should be wide enough to cover the entire root area. This helps keep the ground warm during the frost.
Select a frost cloth based on the predicted temperature. Some frost cloths only provide an extra 4 degrees of warmth, while others provide 8 degrees.
Lay the frost cloth directly over the hibiscus plants. It is okay if the cloth touches or lays on top of the plant. The cloth must reach the ground on all sides.
Set weights on the bottom of the frost cloth to secure it to the ground.