Swamp rose mallow

Sun

Full sun gives the strongest stems and most flowers; tolerates light shade but flowers less freely.

Water

High; keep the root zone consistently moist. Established plants tolerate brief flooding, but prolonged drying causes wilting and bud drop.

Soil

Moist to wet, fertile soil rich in organic matter; tolerates clay and a range from slightly acidic to slightly alkaline.

Height

3-7 ft (0.9-2.1 m)

Spread

2-4 ft (0.6-1.2 m)

Flowers

Summer to early autumn; large white or pink flowers, usually with a dark crimson eye. Each flower lasts about one day, but buds open in succession.

Foliage

Large, alternate green leaves, oval to shallowly lobed, often with pale, softly hairy undersides; dies back after frost.

Growth

Fast during warm weather; forms a substantial clump over several seasons.

Care needed

Medium

• Water deeply whenever the soil begins to dry; do not let newly planted roots dry out.
• Work compost into the planting area and top-dress with compost each spring.
• Apply a balanced, slow-release fertiliser in spring if growth is weak or the soil is poor; avoid heavy nitrogen feeding.
• Mulch with 2-3 in (5-8 cm) of organic material to conserve moisture, keeping it clear of emerging shoots.
• Support tall stems early in exposed gardens, using a plant ring or discreet stakes.
• Mark the crown over winter so you do not damage its late-emerging shoots while planting nearby.

Pruning. In late winter or early spring, cut dead stems to 4-6 in (10-15 cm) above the ground before new shoots develop. Remove spent flowers if you want a tidier appearance or less self-seeding.

Late winter

Cut back dead stems, leaving short stubs to mark the crown.

Spring

Top-dress with compost and renew mulch without covering the crown.

Late spring

Plant or divide once growth starts and the soil warms; allow for its slow emergence.

Early summer

Install supports where needed and check young leaves for feeding damage.

Summer

Water during dry spells and remove spent flowers if desired.

Autumn

Leave sound stems standing for winter structure, or remove diseased material after frost.

• Plant at the back of a sunny, moisture-retentive border for large late-season flowers above lower perennials.
• Use beside a pond or in a bog garden, with the crown at the soil surface rather than submerged.
• Combine with switchgrass and Joe-Pye weed for a tall, informal planting with contrasting flower and leaf shapes.
• Group several plants in the moist lower part of a rain garden where there is room for their mature spread.

Garden styles it suits: Bog garden, Wildlife garden, Pollinator garden, Cottage garden, New perennial (prairie) and Modern tropical.

Plant it with: Cardinal flower, Swamp milkweed, Blue flag iris, Joe-Pye weed, Switchgrass and Royal fern.

Wildlife: Flowers provide pollen and nectar for bees, including specialist hibiscus bees in its native range, and may attract hummingbirds in North America. Leaves feed several native insects.

• Hibiscus sawfly larvae can skeletonise leaves in parts of North America; inspect leaf undersides and hand-pick larvae while infestations are small.
• Japanese beetles chew flowers and leaves where established in North America; hand-pick into soapy water and avoid placing beetle traps beside the planting.
• Drought causes wilting, scorched leaves and dropped buds; water deeply and mulch to keep soil moisture steady.
• Leaf spots may develop in humid weather; remove badly affected leaves, clear diseased debris and water at soil level rather than over the foliage.

Hibiscus moscheutos is not known to be toxic to cats, dogs, horses or people; no part is recognised as seriously poisonous. Eating large amounts of plant material can still cause digestive upset, and garden plants treated with pesticides should not be eaten.

• Rose of Sharon (Hibiscus syriacus)

  A woody shrub with persistent branches and generally smaller flowers; swamp rose mallow dies back to the ground each winter.

• Scarlet rose mallow (Hibiscus coccineus)

  Usually has scarlet flowers with narrower, separated petals and deeply divided, finger-like leaf lobes.

• Tropical hibiscus (Hibiscus rosa-sinensis)

  A frost-tender woody shrub with glossy leaves that remains evergreen in warm climates; swamp rose mallow is a cold-hardy, winter-dormant perennial.

The common name refers to its wetland habitat and large, rose-like flowers.

Propagation. Sow seed in spring after lightly nicking the hard seed coat and soaking it overnight. Divide established clumps carefully as shoots emerge in spring, or take softwood cuttings in late spring or early summer. Named cultivars and hybrids may not come true from seed.

Accepted botanical name

Hibiscus moscheutos

In the US and Canada

Native in Canada and the lower 48 states.

Sources: GBIF (CC BY 4.0) and USDA PLANTS. The care and design notes are LandscapeGPT's own.