Here's How to Enjoy the Tropical Look of Hibiscus, Even Where It Freezes
Not many other summer-blooming plants can boast such large and brightly colored flowers as tropical hibiscus (Hibiscus rosa-sinensis). They look dazzling all through the summer months and even into fall, and make especially eye-catching additions to container gardens. Unfortunately, they can't tolerate freezing temperatures, so if you live in colder regions of the country, you'd have to treat these beauties like annuals that last only for one season, or bring them inside for the winter. However, there are other kinds of hibiscuses that are just as gorgeous as their tropical counterparts, but much hardier, so they will thrive year after year in northern climates.
Can Tropical Hibiscus Survive Freezing Temperatures?
Native to warmer regions of Asia and the Pacific Islands, tropical hibiscus is only hardy in Zones 10-11 where the temperature generally doesn't dip below freezing (32°F). That means it won't survive outdoors in a winter that gets colder than that. This shrubby plant can survive an occasional frost but its stems and leaves may die back a bit. As long as the roots don't freeze, however, you can prune the dead parts away and new growth will sprout in spring.
In areas with long spells of freezing weather, your best bet for enjoying the tropical look of hibiscus in your garden is choosing a hardy type, most of which can be grown where temps can get as low as -20°F (Zone 5 and above). There are several hardy hibiscus species, but the one that has flowers that look most like those of the tropical species in terms of colors, size, and shape is known as rose mallow (Hibiscus moscheutos). Although this perennial hibiscus tends to bloom later in summer than its tropical cousin, some varieties can even produce flowers as big as dinner plates!
How to Grow Perennial Hibiscus
Similar to other perennial plants, rose mallow usually dies back completely to the ground in winter. Just cut back the stems to a few inches in height in late fall or early spring, and you'll see new shoots emerge when weather warms again. Often, it is slow to push out fresh growth, especially during cold springs, so gardeners often worry it's dead. But just be patient and it should make an appearance by late spring or even early summer.
Perennial hibiscus has similar care needs to tropical hibiscus. Both plants will perform best in full sun and need plenty of water to thrive. It's best to never let the soil around either hibiscus dry out completely, which often will mean watering them daily. They might even need a drink twice a day if your region is especially hot and dry or you're growing them in a container. Adding an inch-thick layer of mulch or compost around your hibiscus will also help the soil hold on to more moisture.
With enough water and sunlight, perennial hibiscus will usually grow about five feet tall (its tropical counterpart can tower over 10 feet tall), but there are also several varieties that stay shorter to about three or four feet. From late summer into fall, it will produce beautiful blooms in a wide range of pinks, reds, and pure white (tropical hibiscus produces even more colors, like yellow and purple).
In just about any region of the U.S., you can grow big, beautiful hibiscus flowers. Just double-check your area's hardiness zone to make sure that you choose the type, either tropical or hardy, that can make it through your winter's worst weather.