Grow hibiscus to get double takes on your yard

Looking for a plant that will knock off socks with showstopping bloom, while supporting pollinators and other native wildlife? Consider hibiscus.

To most people, hibiscus is a tropical plant, and it’s true that most of the 200 species of hibiscus grow in Asia and are too tender for Chicago.

“It may be a surprise, but there are hibiscus species that are native to Illinois and winter-hardy in the Chicago area,” said Sharon Yiesla, plant knowledge specialist in the Plant Clinic of The Morton Arboretum. “And they do have those big, five-petaled, tropical-looking flowers.”

Two species of hibiscus, common rose mallow and swamp rose mallow, are both native to wetlands and moist areas of eastern North America. “They are good choices for a low spot in the yard where water collects or for a rain garden,” she said. “These are not drought-tolerant plants. In dry weather, they will need to be watered, and they need mulch over their roots.”

Both plants are large perennials that can grow 3 to 7 feet tall and 2 to 4 feet wide at maturity. “Because they can get so big, hardy hibiscus can have as much presence in the garden as shrubs, but they will die back to the ground in winter,” Yiesla said.

They often are slow to sprout and start growing in spring, but once they do, they grow fast. To keep the plants more bushy than lanky, pinch them back in spring and early summer.

Hardy hibiscus plants will tolerate a little light shade, but they will flower best in full sun and will be most healthy in a site with good air circulation. Each of the flowers lives only for a day or two, like a daylily, but the plants will keep opening new blooms over a long period, sometimes from July to September.

Common rose mallow (Hibiscus moscheutos) has flowers that can be 6 to 9 inches across, usually in shades of white, pink and red with a distinct red center. A number of cultivated varieties, or cultivars, have been selected or hybridized from Hibiscus moschuetos. At the Arboretum, several of these cultivars can be seen planted in the evaluation beds near Godshalk Meadow on the West Side. A white variety, Luna™ white rose mallow (Hibiscus moscheutos ‘PAS304889′), is growing in the Celebration Garden in The Grand Garden.

Swamp rose mallow (Hibiscus palustris) is native to the Chicago region, as well as other areas from Kentucky to Canada. It also has pink to white flowers, although they’re a little smaller — just 4 to 6 inches across. “They’re still large enough to make a splash,” Yiesla said. Swamp rose mallow can be seen blooming in mid-to-late summer among the other native plants by the Arboretum’s Meadow Lake.

Both common rose mallow and swamp rose mallow attract bees, including the specialist pollinator rose mallow bee, as well as offering nectar to hummingbirds and butterflies. Caterpillars of at least 28 species of butterflies and moths use them as host plants.

The foliage of hardy hibiscus is sometimes a target for whiteflies, aphids and Japanese beetles. Still, “they are generally easy plants to grow, if you have moist, fertile soil for them,” Yiesla said. “And people will do a double take when they see those big, Hawaiian-looking flowers.”

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.