Tropical hibiscus, the sun-loving accents that bring flair to summertime displays, grow year-round in warm climates and as tropical annuals in colder regions. Cold-hardy hibiscus have a more versatile range, generally perennializing in USDA zones 4 or 5 through 9 for years of high color.
Hibiscus that come back every year include rose mallow and rose of Sharon. While different species, both fall into the catchall moniker “hardy hibiscus,” though it most often refers to rose mallow.
Rose mallow brings the tropical look to the perennial garden with dinner-plate-sized flowers. Unlike tender tropical hibiscus, hardy hybrids stem from North American native mallows (H. moscheutos, H. laevis, and H. coccineus), with adaptability, durability, cold hardiness, and unique color blends.
Rose of Sharon (Hibiscus syriacus) is a vigorous shrub with characteristically showy hibiscus blooms. It’s larger in stature than the perennial mallows, with somewhat smaller flowers. Some varieties produce abundant seed pods that readily reseed and become invasive. Sterile or seedless cultivars are available to reduce the spread (although there is discussion about sterile cultivars of invasive species and their impacts on the surrounding ecology).
Rose Mallow Overview
Durable perennials flourish in sunlight, showcasing bright summer flowers.
Hardy hibiscus are low-maintenance, easy-care growers. Rose mallows are hardy in USDA zones 4 or 5 through 9. They show the best flowering and stem strength in full sun, with at least six hours of sunlight daily. They also grow in partial shade.
Mallows prefer organically rich soils but adapt to various types given regular water. The moisture-loving plants grow naturally in wet areas. They withstand short dry spells, but in prolonged drought, stress leads to susceptibility to insect damage from Japanese beetles and hibiscus sawflies.
Give them a heavy layer of mulch for moisture retention and overwintering. In spring, new growth is slow to appear, but once it does, it emerges quickly for summer foliage and flowering.
The robust perennials bloom in the heat of summer through early fall. Each flower opens only for a day, but with abundant buds, the flowering is continual.
Showcase rose mallow in the perennial border, rain garden, native planting, bog, and container display. The bright petals and prominent stamens attract pollinators.
Native Species
While easily recognized by their similar flowers, North American native mallows are diverse in color, form, and habitat. The most popular are H. moscheutos and H. coccineus, adaptable selections with showy blooms.
Swamp
This vigorous native features stunning blooms from July to September.
Swamp hibiscus is a vigorous native North American species that grows along streambanks, moist woodlands, swamps, and marshes across the eastern and central United States. Plants reach three to seven feet tall with a rounded habit.
Six-inch flowers with white and pink overlapping petals emerge from July to September. Each bloom has a contrasting reddish-purple throat and prominent stamens. At peak bloom, plants may yield as many as 20 flowers per day.
Scarlet
This native plant showcases striking scarlet flowers and tall stalks.
Scarlet rose mallow, or Texas star hibiscus, features large scarlet flowers with five broad petals swirling around a showy central column of stamens. The red petals of H. coccineus are precisely cut and pointed on stalks that reach six to eight feet tall. Foliage is dark green and deeply palmate with serrated edges.
This native mallow grows along roadside ditches, marshy areas, and wetland edges. It prefers moist soils but adapts to both wet and dry conditions.
‘Halberdleaf’
This hardy plant attracts pollinators with lovely pink and white blooms.
H. laevis occurs naturally in southeastern Canada and the eastern and central U.S. Its pretty pink and white flowers top bright green, erect stems. Fresh green leaves have three lobes with serrated edges.
‘Halberdleaf’ is hardy to zone 4 and an excellent naturalizer for pollinator gardens, wetland margins, or moist woodland edges. It is a host plant for the gray hairstreak butterfly and straight-lined mallow moths.
Hairy-Fruited
Hibiscus wildflowers feature charming blooms and thrive in wet soils.
This large wildflower’s original growing range is the southeastern U.S., where it naturalizes in wet soils and forms colonies in ditches and moist woods. H. lasiocarpus has white or pink blooms with dark magenta eyes atop upright stems.
Medium-green leaves are long with slightly toothed margins. The species gets its name from fuzzy leaves, stems, and seeds.
Velvet
This native mallow features large pink blooms and attracts bees.
H. grandiflorus has maple leaves flocked in velvety gray. Its distinct pale pink petals reach ten inches wide, followed by hairy seed pods that persist through winter for extended interest and forage for birds. Native bees flock to the summer blossoms.
This hardy mallow is a southeastern U.S. native and grows in marshy, brackish areas. It’s a good fit for boggy wetlands and naturalized gardens and adapts to dry spells. It has a warmer range and is hardy in zones 6 to 9.
Popular Varieties
With so many delicious cultivars available, choosing among the Moscheutos and native hybrids is a delightful challenge. From bold and bright to soft and pastel, the huge blooms swirl among compact, well-branched forms.
‘Midnight Marvel’
This variety features stunning red blooms and colorful foliage.
‘Midnight Marvel’ is a favorite with crimson blooms that stand out amongst dark foliage. Its maple-shaped leaves are violet and olive green and turn vivid orange in the fall. Black-red buds open to substantial ten-inch red flowers with yellow stamens.
‘Midnight Marvel’ has a mounded, compact habit at three to four feet tall with good branching. Buds occur along the length of the stems for a heavy succession of tip-to-toe blooms.
‘All Eyes on Me’
The cultivar showcases lush pink petals and vibrant centers.
‘All Eyes on Me’ has tissuey pale pink petals with brushed magenta-red centers. The billowy petals overlap heavily and cover the compact, three-and-a-half-foot-tall plants. Pretty-in-pink buds and eight-inch disks cover dark green foliage.
This variety is part of Walters Gardens’ Summerific® series and features robust growth and flowering. The plants are full, vigorous, and loaded with buds.
‘Mocha Moon’
This plant features striking white blooms with scarlet centers.
‘Mocha Moon’ has cups of pure white petals with painted scarlet centers. Its maple-leaf foliage is striking in bronze and mahogany.
‘Mocha Moon’ is vigorous and bushy with good rounding at three to four feet tall. Its compact size and upright branches accommodate small spaces and potted arrangments.
Lime green sepals persist and stand out in the darkness for more of that mallow contrast the garden needs.
Rose of Sharon Overview
This shrub offers vibrant blooms and striking vertical interest.
Rose of Sharon (also called althea) brings vertical interest and a carefree habit with shrubs that reach eight to twelve feet tall. The growing conditions are largely similar among the genus, and they’re usually hardy in zones 5-9. Like their mallow relatives, they grow best in full sun to partial shade with moist, well-draining soils. The adaptable growers tolerate heat, humidity, and coastal and urban situations.
Rose of Sharon is indigenous to India and China and began growing in the U.S. in the 1700s for its ornamental qualities. It begins blooming in July, and continues until frost with hollyhock-like flowers. Its showy petals in pink, white, and purple often have a dark central eye, and the single or double blooms have ruffly appeal. Attractive foliage is usually maple or heart-shaped on vase-shaped, upright, and columnar forms.
The flowering shrub makes a visual impact in groups and hedges, as foundation accents, and border specimens. It takes pruning well and trains as an espalier.
Popular Varieties
Many rose of Sharon cultivars are available in varying sizes, forms, and colors. They offer exciting twists on the vintage favorite and tend to reseed less vigorously.
‘Blue Chiffon’
This cultivar features elegant lavender-blue blooms and lush foliage.
‘Blue Chiffon’ stands out among the group with watery, lavender-blue blooms and frilly centers. The rich blue blossoms, dark green foliage, and rounded habit give this cultivar an elegant structure.
‘Blue Chiffon’ received the Royal Horticultural Society’s Award of Garden Merit for its ornamental value and vigor. Plants produce few seeds, so spreading is less of a concern than with heavy seeders. The Chiffon series houses pink and white cultivars with the same tissuey petals in bright shades.
‘Purple Pillar’
This columnar beauty features vibrant purple blooms all summer.
‘Purple Pillar’ boasts a slender, columnar frame with upright branching. At maturity, the column reaches 10 to 16 feet tall and four to five feet wide. It’s a fit for sunny corners, foundation cut-ins, containers, and the mixed border where height and color are assets.
Purple petals with magenta centers line the stems in summer through early fall. Prune plants in the spring if needed for sizing.
‘Lil’ Kim’
This petite variety blooms generously with white flowers throughout summer.
‘Lil’ Kim’ is a miniature althea, and everything about it is smaller except for its floriferous nature. Plants grow only three to five feet tall. Bright white, ruffly flowers with painted red centers last longer than most at about three days each.
The small cultivar buds and blooms along the entire length of the stem, making for an extended season. It has a full, rounded habit and graceful form that is well-suited to container culture.
