Common names: Hardy hibiscus, rose mallow, swamp mallow, wild cotton, Eastern rose mallow
Botanical name: Hibiscus moscheutos, hybrids, and cultivars
Hardiness: Zones 4–9
Conditions: Hardy hibiscus prefers sunny spots where soil is rich and drains well but remains damp. In spite of the moniker swamp mallow, boggy soil that remains waterlogged is not to their liking. Mostly they tolerate shade for part of the day but prefer full sun.
Bloom time: Midsummer to fall
Height: 3–8 feet fall
Best feature: With imposing stature and huge, dramatic, trumpet-shape flowers, hardy hibiscus is seldom overlooked. Butterflies and hummingbirds flock to the flowers for nectar. Ideal for damp soils and near water.
LOOKING FOR A MAJOR player for your summer garden that is sure to elicit oohs and aahs? Look no further than imposing hardy hibiscus (Hibiscus moscheutos) with its exotic, sometimes almost dinner plate-size blooms up to 12 inches across. This southwestern native forms vigorous bushes clad with medium green, mostly heart-shape, toothed 3- to 8-inch leaves on short stems; some selections have interesting cut foliage and/or red-veined leaves. Hardy hibiscus is commonly known as rose or Eastern rose mallow, swamp mallow, or wild cotton. True mallows (Malva spp.) have blooms with a similar structure; wild cotton refers to their look alike cousins, cotton (Gossypium). Hollyhocks (Althaea), tree mallow (Lavatera), and okra (Abelmoschus) are also closely related; all belong to the botanical family Malvaceae. Common to this clan, the stamens form a central “staminal” column around the pistil or style (female part).
Flowers: The showy five-petal flowers are unusually large, up to 12 inches across, mostly pink, white, or red and often with a dramatic central eye. Modern selections embrace a wider color palette that includes mauves and plums, hot and bubblegum pinks, along with ruffled, striped, and color-swirled petals. The petals, which often overlap, have a delicate, tissue-paper look. The blooms are popular sources of nectar for hummingbirds, butterflies, and bees; seed-eating birds, including Northern bobwhites (Colinus virginianus); and some water birds depend on the seeds for winter food.
How to grow: Given conditions to their liking, hardy hibiscus (Zones 4–9) are long-lived perennials that require little care. They do best in full sun but tolerate a little shade for part of the day. Soil should be fertile and well-drained, although in the wild they may be found growing in swampy ground. In cultivation they thrive in damp, humus-rich, moisture-retaining soil but not with permanently wet feet. The tall, spent stems can remain all winter or may be cut down; new growth is slow to emerge in late spring, maybe even after Memorial Day in cold regions. Once begun, growth is rapid. If necessary, prune young stems to control height and encourage bushiness. Japanese beetles are the main insect pests to attack hardy hibiscus. They chew the leaves, buds, and flowers, leaving a tattered mess behind. Hand-pick, spray with a strong water jet, or apply pesticide to control them. Japanese beetle traps may encourage more of them to arrive in your garden. Be sure to stake tall cultivars, especially in windy sites if necessary.
Propagation: Seed and cuttings are the most successful means of propagation for hardy hibiscus. Division is difficult and seldom works well. Seed is readily available in the marketplace, or you can harvest your own. It is wise to nick (scarify) the seed coat with a file or knife prior to sowing to enable the embryo to take up water and germinate. Take 3- to 4-inch-long cuttings of soft young growth; root in moist sand, perlite, or other rooting medium. Rooting hormone speeds up the production of roots, which may take several weeks to emerge.
Where to grow: These dramatic plants show off best at the back of flower borders or in front of a fence, hedge, or tall shrubs. They are also valuable in informal settings—perhaps to accent a rustic post-and-rail fence, or as a summer hedge. In perennial and flower gardens, tall selections of hardy hibiscus can be used to provide a strong background for less-imposing perennials, including great bellflowers (Campanula latifolia) and milky bellflowers (C. lactiflora), queen of the prairie (Filipendula rubra), garden phlox (Phlox paniculata), Jerusalem sage (Phlomis fruticosa), and monkshoods (Aconitum spp.). They tolerate coastal conditions well and are attractive there with tall ornamental grasses and beach roses (Rosa rugosa). In summer, their tropical look equips them to combine well with tender plants, including elephant’s ears (Alocasia spp), shell gingers (Alpinia zerumbet), yesterday-today-tomorrow (Brunfelsia australis), and Persian shield (Strobilanthes dyerianus). In native plant gardens, try yellow wild senna (Cassia marilandica), red cardinal flower (Lobelia cardinalis), blue lobelia (L. siphilitica), and selections and hybrids of purple coneflower (Echinacea purpurea) as companions. Your own color sense will tell you which cultivars are best in your personal color scheme. Look for compact varieties for containers, where they are effective all by themselves as focal points. They are especially attractive in tubs around swimming pools and water features. Hardy hibiscus are not for the faint of heart, but they show off well in so many parts of the garden that it is a shame not to utilize them. See our list, at right, for readily available hybrids and cultivars; you might find several that are just right for that special place you’ve got left in your garden.
Hardy Hibiscus Varieties
Plant breeders have recently increased the wide range of sizes and flower colors of rose mallow. Surely you’ll find at least one selection of these hummingbird attractors for your own garden. Most are hardy in Zones 4–9.
‘Blue River II’ (H. moscheutos, 4–5 feet tall) sports a wide bush of bluish-green foliage and huge all-white flowers from mid- to late summer.
Fleming’s Hardy Hibiscus strain, noted for its upright habit and dissected leaves, includes ‘Fireball’ (4–6 feet tall) with purpleflushed foliage and dark-centered, cherry-red flowers 8–10 inches wide that open from twisted, almost-purple buds.
Compact ‘Fantasia’ (2½ –3 feet tall) produces plenty of purplish-pink, red-eyed flowers.
‘Heartthrob’ (3–4 feet tall) has dramatic dark crimson flowers 8–10 inches across with black eyes; compact and mounded.
‘Jazzberry Jam’ (4–5 feet tall) produces robust, ruffled, deep rose flowers 9 inches wide from midsummer into fall. Bushes may reach 6–7 feet wide.
‘Kopper King’ (3–4 feet tall) is noted for its attractive purple foliage that shows off red-eyed pink flowers to perfection. ‘Lady Baltimore’ (3–4 feet tall) is a tried-and-true cultivar that in late summer sports fragile-looking, candy-pink 6- to 8-inch-wide flowers, accented with a cerise eye.
‘Lord Baltimore’ (4–5 feet tall), an older cultivar, has lightly ruffled, bright red flowers as large as 10 inches across. Pinkflowered Disco Belle Pink is similar.
Luna Series includes very heat-tolerant, dwarf selections 2–3 feet tall (Zones 5–9). Flowers reach 6–8 inches wide on bushy, branching plants. ‘Luna Rose’ bears strong rosy pink flowers; ‘Luna Pink Swirl’ has white flowers swirled with pink, around a cherry-red center. ‘Luna White’ and ‘Luna Red’ also are available. ‘Old Yella’ (3–4 feet tall) was the first yellow hibiscus. Pale yellow flowers, to 12 inches across, accented with a burgundy eye. Early summer through fall. Summerific hybrids (4–5 feet tall) are noted for their very long bloom time. ‘Berrylicious’ has crimson-eyed, mauve flowers; considered an improvement on ‘Fantasia’ in habit. ‘Cranberry Crush’ makes very wide plants covered with purplish dark-green foliage and scarlet-red, 8-inch flowers. ‘Cherry Cheesecake’ has dark, maple-like foliage, along with 7–8-inch wide flowers with overlapping white petals tip
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