Swamp rose mallow is a large, beautiful addition to a rain garden or other wet areas of a landscape. The showy pink or white flowers with red centers will attract a number of pollinators, including hummingbirds, from midsummer to early fall. This species is native to the Chicago region according to Swink and Wilhelm’s Plants of the Chicago Region and current research.
Size and method of spreading:
Swamp rose mallow grows to 3 to 7 feet tall and spreads to 2 to 4 feet wide at maturity. It often spreads by self-seeding.
Native geographic location and habitat: (include C-value if appropriate)
Swamp rose mallow is native to wet areas of the Eastern and Southern United States. C- value: 7.
Attracts birds or pollinators:
Swamp rose mallow attracts bees, including the specialist pollinator rose mallow bee, as well as hummingbirds and butterflies. Caterpillars of at least 28 species of butterflies and moths use swamp rose mallow as a host plant. Whiteflies, aphids, and scale sometimes feed on the foliage of swamp rose mallow.
The leaves of swamp rose mallow occur singularly along the stems (alternate arrangement), and are attached by a stalk (petiole) that has two leaflike stipules at the base. The leaves may have three to five lobes or be lobeless. The edges of the leaves have teeth that may be slightly rounded (crenate to dentate margins). The upper leaf surfaces are nearly hairless to hairless (glabrous) and medium green to yellowish green in color, whereas the lower surfaces are grayish or whitish from the short hairs that cover them (canescent). Swamp rose mallow leaves are widest at the base and narrow to pointed tips (ovate with acute apices)
Similar to other hibiscus flowers, swamp rose mallow has five petals, five leaflike sepals under the petals, approximately 12 thinner leaflike structures (bracts) under the sepals. The male stamens are fused together at their bases forming a column (monadelphous stamen) through which the female (pistil) rises. Only the top of the female (the stigma) is usually visible. This is the typical arrangement of gender structures in the mallow family. The petals of swamp rose mallow can be pink or white, and the bases are often crimson-colored. The petals are also large and somewhat egg-shaped with the narrowest end at the base (obovate). Like the leaves, the sepals are ovate with acute apices; however, they are united at the base.
The fruit of swamp rose mallow is dry and opens into five segments to release rings of seeds (capsule). Each capsule is almost spherical (globoid to ovoid) but with a pointed top (short-beaked). It is dark brown, almost mahogany, in color. The sepals and bracts from the flowers will persist when the fruit is present, even after it opens to release the seeds.
Swamp rose mallow is best grown in moist, full sun conditions with good air circulation. If a bushy appearance is desired, pinch back growth when the plant reaches 8 inches, then again when it reaches 1 foot. Deadheading can improve the appearance of swamp rose mallow.
List of pests, diseases, and tolerances:
Swamp rose mallow can have some minor disease issues with blight, canker, leaf spots, and rust. It has some tolerance for salt, clay soils, and occasional flooding. Japanese beetles can cause severe damage to the foliage of swamp rose mallow.