Last Updated on September 15, 2022 by Plant Mom Care
Swamp rose-mallow or Hibiscus moscheutos, a species of plants in the Malvaceae family, is commonly found in wetlands and along streams and rivers of North America.
This perennial wildflower is around 3 – 7 feet tall and with short flowering stalks along the upper part. The light green stem is cylindrical and the leaves vary in shape from three-lobed to lance-like, about 3 – 8 inches long and 2 – 4 inches wide, with thin 2 – 5-inch long reddish-green or light green petioles. The surface on the upper leaf is yellow-green to medium green and smooth, while the pale green lower surface is canescent.
The flowering stalks are about 1.5 – 3 inches long, bearing one leaf and one flower. The flowers are 4 – 6 inches long and wide and consist of 5 petals and 5 yellow-green sepals. Each short-lived flower opens only for a day or two and fades after pollination. Usually, only 1 – 2 flowers bloom on a plant together at once.
The flowering season is from mid-summer to early autumn and lasts for about a month. Flowers are white, red, pink, or bi-colored, often with a contrasting deep maroon eye. The globoid-ovoid seed capsules are about 1–1¼ inch long containing a circle of seeds that are flat kidney-shaped and smooth. This wildflower naturally spreads by reseeding.
It hosts larvae of the gray hairstreak, the common checkered skipper, the pearly wood nymph, and the Io moth and attracts nectar-feeding insects and birds that help pollinate the flowers. Red-winged Blackbirds often use the plant as nesting sites and the seeds provide food for birds in winter.
This is a popularly cultivated plant, with several hybrids being developed and sold by commercial nurseries and garden centers. This plant is good to grow in borders, rain gardens, marshes, in large containers, around ponds and streams, and as a screen. They also look lovely as hedges in the summer.
Swamp Rose Mallow Light Requirements
This plant prefers full sunlight (6 hours daily). In hot summers, it might be necessary to provide shade in the afternoon to prevent leaf scorch. While this plant tolerates partial shade, too much shade might make plant growth leggy and susceptible to pest infestations.
Swamp Rose Mallow Watering
This plant loves water and often stops flowering in dry soil. It needs deep watering 2 or 3 times each week in warm weather. Once it is actively growing during its first season, watering is particularly important. However, the plant must immediately be watered if it displays signs of wilt. Early morning watering gives the plant enough time to become dry and prevents fungal rots and other diseases. This plant dies and becomes dormant in winter, water just enough to dampen the soil until new growth appears in spring.
Swamp Rose Mallow Humidity
This plant can handle any humidity level, from average to high, and is immune to the heat and humidity in the Southern states of the US.
Swamp Rose Mallow Temperature
This plant grows well in hardiness zones of 5 – 9, with temperatures between 25 – 95°F.
Swamp Rose Mallow Soil
It grows well in rich soil amended with organic compost or manure. Mulch the soil about 2 or 3 inches around the plant to prevent weeds and cool the roots. Since it prefers wet soil, it can thrive in low and wet areas near streams or ponds. However, it can tolerate different types of soil if it is watered well.
Swamp Rose Mallow Repotting
This plant can grow for 2 – 3 years before it gets root-bound. Repot in late winter using potting soil and move it to a larger well-draining pot.
Swamp Rose Mallow Propagation
This plant can be propagated from seed, cutting, and crown division.
Propagation from seed
Plant the seeds in biodegradable pots under a temperature of not less than 72°F in early spring. The seeds germinate rapidly. Choose the larger seedlings as they are easy to handle and plant the pots outside in your garden in early summer.
Propagation from cuttings
4-inch long softwood or stem cuttings should be cut away when new growth emerges in spring. Remove any flower buds on the cuttings. Lightly scrape the bark at the bases and dust with rooting powder. Put 3 cuttings together in biodegradable pots under a temperature of more than 72°F. Rooting starts within 3 weeks, plant the pots directly in your garden when new growth appears.
Propagation by division
Divide the plant during spring, when soft, new growth appears. Dig the plant up with angled cuts into the ground to raise the plant out without damage and divide it with a shovel or sharp knife. Let the exposed cuts become dry before replanting. Replant the divisions at the same level as the parent plant.
Feed the plant in spring, when new growth appears, by sprinkling slow-releasing fertilizer around the root area and then complement this with water-soluble fertilizer in early summer when flower buds start forming.
When new growth emerges in spring, prune down old stems to give way for new growth. Pruning branch tips in early summer will stimulate branching and encourage bushier growth.
Deadheading spent blooms is not necessary unless you don’t want seedpods to form.
In cold climates, mulch your plants after they become dormant to give them extra insulation from the cold. A potted plant can be left outdoors unless temperatures drop below 20°F for a long time, moving the pot indoors to a garden shed or garage until temperatures start warming up again.
Plants growing near each other should have a minimum of 36 inches of space between each other. Crowding impedes air circulation and might result in diseases like leaf spots and rust among others. Also, protect the plant from strong winds that can harm the delicate flowers.
Swamp Rose Mallow Common Problems
This plant is particularly susceptible to sawflies and Japanese beetles. Leaf fungus is also an issue but easy to prevent by cutting away infected leaves and good air circulation.
Spray the plant with insecticidal soap if it is affected by aphids, whitefly, or scale.
Deer might sporadically damage this plant when it grows outdoors.