Hardy perennial hibiscus add the beauty of tropical hibiscus to the garden, but can withstand cold winter temperatures that kill the actual tropical varieties. Here's how to grow hardy hibiscus in your garden!
About Hibiscus
Perennial hibiscus have big, disc-shaped, hollyhock-like flowers that can measure up to 12 inches across. The perennial hibiscus species found in gardens are the result of hybridizing native hibiscus species, including Hibiscus moscheutos (Rose Mallow) and H. coccineus (Swamp Hibiscus). In areas that receive a hard frost, these species will die back to the ground in winter, regrowing in the spring. Dwarf varieties reach only a few feet in height, while standard varieties may grow up to 8 feet tall.
The larger, more shrub-like hardy hibiscus species, H. syriacus (Rose of Sharon), produces an abundance of smaller flowers, but grows into a much larger shrub that doesn't die back to the ground in winter. Depending on variety, Rose of Sharon can reach up to 12 feet tall and 10 feet wide.
Planting
When to Plant Hibiscus
- Rose Mallow and Swamp Hibiscus can be purchased as young plants from nurseries or started from seed or cuttings. They should be planted in the spring.
- Seeds can be sown indoors 12 weeks before the last spring frost. (See local frost dates.)
- Alternatively, seeds can be sown outdoors after the last expected frost date.
- Rose of Sharon are typically purchased as small shrubs.
Choosing and Preparing a Planting Site
- Choose a site that gets full or partial sun.
- Fertile, well-draining soil will produce the healthiest plants. Hibiscus are tolerant of alkaline soils, but will grow best in neutral to slightly acidic soil.
- To avoid breakage of the long stems, plant hibiscus where they won't be exposed to strong winds.
How to Plant Hibiscus
- Plant potted hibiscus plants so that their stems are just at the soil surface.
- Water well at the time of planting.
- The hibiscus species that die back each year can be spaced 2 to 3 feet apart. Consider the potential height and width (up to 12 feet and 10 feet, respectively) of a mature Rose of Sharon before planting.
Care
How to Care for Hibiscus
- Mulch around the plant to retain moisture and to provide winter protection for the roots.
- Water plants deeply and thoroughly, if needed.
- Hibiscus bloom on new wood (this year's growth), so pruning is best done in the spring.
- In early spring, remove dead stems from established plants and apply a balanced fertilizer.
- To encourage re-bloom, remove old flowers before they form seed heads or prune plants back by one third after a flush of bloom is finished.
- Mature plants can be divided in the spring.
Pests/Diseases
- Japanese beetles
- Aphids
- Whiteflies
Recommended Varieties
- Scarlet Swamp Hibiscus (H. coccineus): This plant, also known as Texas Star, has 5-petaled, brilliant-red flowers.
There are many wonderful hardy hibiscus hybrids available. Here are just a few:
- ‘Lord Baltimore’: Red flowers.
- ‘Sweet Caroline’: Pink flowers with dark centers.
- ‘Blue River II’: Beautiful white flowers.
- ‘Kopper King’: Huge pink blossoms with red centers. It’s named for its dramatic copper-colored foliage.
Wit and Wisdom
- The plant has been used to soothe headaches, aching limbs, coughs, and inflammations.
- Hibiscus tea is made from parts of a different type of hibiscus, Hibiscus sabdariffa—also known as Roselle or Florida Cranberry. It's native to West Africa, but is now grown across Central America, the Caribbean, and even Florida.
- In Victorian times, giving a hibiscus blossom to a person meant that the giver was acknowledging the receiver’s delicate beauty. Learn about more about the language of flowers.
