Swamp rose mallow

Perennial

Hibiscus moscheutos

Swamp rose mallow

A hardy perennial hibiscus with flowers up to 20 cm (8 in) across in white, pink or red, often with a dark eye.

  • Full sun
  • 1.5–2.5 m (5–8 ft)
  • 0.5–1 m (2–3 ft)
  • H4 · Zone 8
  • July–September
  • Deciduous

Overview

Swamp rose mallow, also called hardy hibiscus or common rose mallow, is a herbaceous perennial native to wetlands of eastern North America. Tall stems carry broad leaves and huge saucer flowers up to 20 cm (8 in) across from mid summer to early autumn.

It is hardy to about −10°C (14°F) in the RHS rating, and to USDA zone 4 in its native range, but needs long hot summers to flower well; in cool climates it can be shy. It thrives in hot, humid summers and wet soil.

Grow in full sun in rich, moist to wet soil. It hosts many native moth and butterfly caterpillars in North America.

At a Glance

Sun Full sun
Height 1.5–2.5 m (5–8 ft)
Spread 0.5–1 m (2–3 ft)
Hardiness H4 · Zone 8
Flowers July–September
Soil Clay, Loam
Moisture Moist well drained
Habit Rounded, Upright
Water High
Maintenance Easy

Growing Conditions

Min. Temperature -10°C (14°F)
pH Range 5.5–7
Fertility Fertile
Drainage Moderate

Aspect Suitability

  • South-facing
  • West-facing

Site Tolerance

  • Wet soil

Soil Tolerance

  • Clay
  • Loam
  • Acid
  • Neutral pH

Foliage

Persistence Deciduous
Colour Green
Leaf shape / texture ovate

Foliage interest: June–October

Seasonal Timeline

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Flowering
Foliage
Fruiting
Propagate
  • Flowering Jul Aug Sep
  • Foliage Jun Jul Aug Sep Oct
  • Fruiting Sep Oct
  • Propagate Mar Apr May Jun

How to propagate

Ways to grow more Swamp rose mallow:

Division May Easy

You'll need: Spade or sharp knife

  1. Lift or expose the clump as growth starts
  2. Cut into sections, each with roots and healthy buds
  3. Replant at the same depth in improved soil
How long
1 hour
It's worked when
high
Then
Water in well and keep moist while new roots form.
Softwood cuttings May Takes a little care

You'll need: Sharp knife, gritty compost

  1. Take 10 cm (4 in) young shoots
  2. Remove lower leaves
  3. Root in a propagator
How long
15 minutes
It's worked when
medium
Then
Pot on and plant out once established.

Sow in warmth in spring; divide or take softwood cuttings as shoots appear.

Maintenance Calendar

  • May Mark the crown and be patient, as shoots appear late
  • Jun Feed and mulch
  • Jul Never let the soil dry out
  • Aug Check for sawfly larvae and aphids
  • Nov Cut stems to 30–60 cm (12–24 in), leaving them for nesting bees

Garden Design

Works well in: Tropical / Exotic, Wildlife-friendly

Dinner-plate flowers on a hardy perennial give a tropical look in cold gardens. Shoots appear very late in spring, so mark the spot.

Companion planting: Cannas, Grasses, Eupatorium, Hedychiums

Wildlife Value

  • Bees
  • Butterflies
  • Birds

Safety

Not known to be toxic.