Hardy hibiscus are an overlooked group of perennials with tremendous potential for the landscape. Hardy hibiscus are herbaceous perennial members of the genus Hibiscus. They are large-flowered, fast-growing plants reaching up to 15 feet tall and 4 to 8 feet wide. They are close relatives of the tropical hibiscus (Hibiscus rosa-sinensis) seen commonly in the landscapes of southern and central Florida. Unlike their tropical counterparts, however, hardy hibiscus are much more cold hardy, vigorous, and long lasting, and they have larger flowers.
In north and central Florida, these plants emerge from the ground in mid-to-late spring and bloom from late spring through fall. With the exception of some of the herbaceous species, a hard freeze kills the aboveground growth but below-ground stems overwinter and produce new shoots the following spring. Some species require freezing (chilling hours) to release vigorous new growth making them better suited for north and central Florida than for south Florida. Hardy hibiscus prefer full sun or partial shade and any soil that is not too dry. Hardy hibiscus are especially useful in areas where the soil is too wet for other perennials. In the landscape, they are often used as colorful, flowering specimen plants, as borders, or as taller components of perennial gardens. Many are well suited to semi aquatic conditions and can be a great way to plant marshy areas that are otherwise maintenance problems. Some, such as swamp rosemallow (H. grandiflorus), are salt tolerant and are very adaptable to coastal areas. Hardy hibiscus is the perfect centerpiece plant in large mixed containers or planted alone. The bigger the container, the bigger the impact it makes.
Hardy Hibiscus Species
Many hardy hibiscus are native to Florida and the southeastern United States, including comfortroot (Hibiscus aculeatus), scarlet rosemallow (H. coccineus), swamp rosemallow (H. grandiflorus), halberdleaf rosemallow (H. laevis), and crimsoneyed rosemallow (H. moscheutos). These species are worthy of landscape use in their own right. Swamp rosemallow has rich, fuzzy gray-green leaves on a plant that reaches up to 15 feet in height. This species is salt tolerant and can grow in brackish water directly in the tidal zones. Flowers of H. grandiflorus are about 8 to 10 inches across and a clear, soft pink. Flowers of scarlet rosemallow are most commonly a clear red with petals that do not overlap, but the range of forms and closely related species will vary a lot.
Many non-native Hibiscus species are used similarly to native hardy hibiscus, and non of the non-natives mentioned are invasive in Florida (https://assessment.ifas.ufl.edu/). Confederate rose, Hibiscus mutabilis, is an old-fashioned garden plant of the southern United States. This upright, tree like species grows up to 15 feet high and 10 feet wide in freeze-free areas of south and central Florida. In north Florida, heights of 6 to 8 feet are more common due to the annual hard freezes. Large-leaved and coarse-textured, confederate rose begins flowering in late summer, producing 6-to-8inch blooms that open white and fade to pink. One of its most notable features is that white, light-pink, and dark-pink flowers can be found at the same time on any given plant. The most common form is 'Flora Plena' with double flowers. A closely related species, H. paramutabilis, and its cultivar, 'Rubra', are smaller-statured plants (usually 4 to 6 feet in height) with single intense deep-pink to carmine blooms.
Other hardy hibiscus species are grown for food or fiber as well as ornament. African rosemallow (Hibiscus acetosella) has become popular as a foliage color annual in plantings around the United States. H. sabdariffa is a food plant with the common names of roselle, Jamaica sorrel, and Florida cranberry. The main edible part is the fleshy sepal, called a calyx, that surrounds the fading flower and developing seed capsule. The ornamental calyx is bright red and acid and is used to make tea, juice, jelly, or a cranberry-like sauce.
Crimsoneyed rosemallow (Hibiscus moscheutos) and several other species have been used extensively in breeding programs. These hybrids produce spectacular flowers up to 12 inches across in shades of white, pink, and red. Recent breeding programs are supplanting older cultivars such as 'Disco Belle Mix' and 'Southern Belle' with more vigorous cultivars such as those in the Summerific® series as well as other recent, trademarked and patented cultivars. These newer cultivars tend to grow smaller and more compact than the species. The Luna™ series is exceptionally dwarf and available as a seed-produced crop, while others like the 'Vintage' series are produced only by cuttings and offer new tones of deep cerise on dwarf plants. Some cultivars, such as 'Red Shield' and 'Kopper King', have been selected for their foliage.
Characteristics of Hardy Hibiscus
Characteristics of selected hardy hibiscus previously evaluated in north Florida are listed in Tables 1 and 2. Other commercial cultivars include 'Anne Arundel', 'Cerise', 'Cranberry Punch'™, 'Crimson Wonder', 'Crown Jewels', 'Davis Creek', 'Flare', 'Giant Maroon', 'Pink Clouds', 'Plum Crazy', 'Raspberry Rose', 'Red Flyer', 'Robert Fleming', 'Royal Gems', 'Sweet Caroline', and many others.
Care of Hardy Hibiscus in the Garden
The major insect pest of hardy hibiscus is the caterpillar-like larva of the hibiscus sawfly, Atomacera decepta. Several of these larvae often feed on the same leaf or plant and can quickly defoliate the entire plant. Other pests include whiteflies, mealy bugs, grasshoppers and spider mites. The primary diseases are various leaf spots caused by Cladosporium, Cercospora, Phyllosticta, and other fungi.
Characteristics of native or species forms of hardy hibiscus previously evaluated at UF/IFAS facilities.
Characteristics of hardy hibiscus cultivars previously evaluated at the UF/IFAS North Florida Research and Education Center, Quincy, FL.