Persicaria amphibia

RHS Plant Profile
amphibious bistort

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Other common names

amphibious knot grass, floating polygonum, ground willow, water buckwheat, willow grass, heart's ease, water willow, canwraidd y dŵr

Synonyms

Polygonum muhlenbergii
Polygonum amphibium

Plants for pollinators
Aquatic Bogs Herbaceous Perennial
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A perennial marginal or aquatic plant, with long, slightly glossy green leaves with paler green veins. Produces short spikes densely packed with tiny pink flowers, from mid summer to early autumn

Position

Full sun, Partial shade

Soil Types

Loam

Max Height

0.1-0.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
0.1-0.5 metres

Growing Conditions

Loam
Moisture
Moist but well–drained or Poorly–drained
pH
Acid or Alkaline or Neutral

Position

Full sun Partial shade
Aspect
East–facing or South–facing or West–facing
Exposure
Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H7

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Polygonaceae
Native to GB/Ireland
Yes
Foliage
Deciduous
Habit
Submerged, Floating
Genus
Persicaria can be annuals, herbaceous or evergreen perennials or sub-shrubs with simple leaves and small bell-shaped white or pink flowers in long-lasting spikes or panicles
Name Status
Correct

How to Grow

Cultivation

Grow as a marginal or bog plant in moist soil, or as an aquatic plant at up to 80cm depth. Flowers best in full sun. Lower young aquatic plants in stages, allowing them to grow at each stage until the leaves float on the surface of the water. Divide regularly to avoid congestion. Has the potential to become a nuisance if not managed well. See aquatic weeds, pond plants and bog gardens for further advice

Propagation

Propagate by seed or by division

Suggested planting locations and garden types

  • Wildlife gardens

Pruning

No pruning required

Pests

Generally pest-free

Diseases

Generally disease-free