The tropical or Chinese hibiscus is least tolerant to winter cold.
The extent and severity of cold temperatures determines if any species of hibiscus survives or dies in winters across the United States. Numerous species of hibiscus grow in gardens, but not all tolerate frosts or survive the extremely cold winters in the northernmost U.S. or Canada. The most useful tool in determining winter survivability, or winter hardiness, is using the U.S. Department of Agriculture plant hardiness zone map. Based on the winter zone designation, you can learn which hibiscus species survive the winter your in area. Does this Spark an idea?
Chinese Hibiscus
Tropical hibiscus cultivars display many vivid color combinations.
With origins in China, but grown and extensively hybridized across the tropics, Chinese hibiscus (Hibiscus rosa-sinensis) does not survive winter temperatures much below 32 degrees Fahrenheit. It's best grown permanently outside in garden beds only in USDA zones 10 and warmer. Frosts kill back the evergreen leaves, and subfreezing temperatures kill back branches until the cold penetrates to even kill the underground roots. These tropical hibiscus may be grown as houseplants. Move them outdoors in summer to prosper in the heat, rains and humidity, but relocate them indoors from fall to spring.
Hardy Hibiscus
White flowers of a hardy hibiscus
Also called rose mallow or swamp mallow, the hardy hibiscus (Hibiscus moscheutos) dies back to its roots when subfreezing temperatures occur, but resprouts in spring. Grow hardy hibiscus in USDA zones 5 through 11. The upright stems become somewhat woody at their bases and produce their large flowers by late summer and into fall up until killing frosts. In regions where winter cold isn't severe, gardeners prune back hardy hibiscus stems in winter and allow new stems to rejuvenate in spring.
African Rosemallow
Grown for its deeply cut, maplelike leaves, the African rosemallow (Hibiscus acetosella) grows as an annual and dies after it flowers and sets seeds, or is killed by frost. It will not return the next year. Any seeds left in the soil may sprout the next spring, however. In USDA zones 10 and warmer, the seeds continually germinate year round, so that there never is a bare spot once one African rosemallow plant withers away.
Rose of Sharon
Rose of Sharon flower with red center
Another cold-hardy hibiscus is the woody shrub more commonly called rose of Sharon (Hibiscus syriacus). Grow this species in USDA zones 5 through 9, where winters always drop below freezing and cause a leafless dormancy. Rose of Sharon flowers tend to look more funnel- or trumpet-shaped, since their petals aren't wide opening.
Scarlet Rosemallow
Native to swamps across the American Southeast, scarlet rosemallow (Hibiscus coccineus) is sometimes called Texas star because of the five massive pointy red petals in each blossom. Grow it in USDA zones 6 and warmer. Just like with hardy hibiscus, frost kills back the stems, otherwise it remains an upright shrub over winter.
Tags: USDA zones, hardy hibiscus, USDA zones warmer, zones warmer, African rosemallow, called rose