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Persicaria polymorpha - Knotweed

Persicaria polymorpha

4,5/5
33 reviews
3 reviews
1 reviews
2 reviews
3 reviews

Well, a Policarpa polymorpha is not a knotweed. I hope I didn’t get a knotweed because knotweeds produce suckers, which is not the case with the polymorpha. We’ll see. Otherwise, the young plants arrived in good condition.

Christelle , 27/05/2025

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This plant carries a 12 months recovery warranty

More information

Value-for-money
Persicaria polymorpha forms a large clump, reaching a height of 2m (7ft), covered in mid-summer with countless spikes of branching flowers which are pure white.
Height at maturity
2 m
Spread at maturity
1.20 m
Exposure
Sun, Partial shade
Hardiness
Hardy down to -29°C
Soil moisture
Moist soil, Damp soil
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Best planting time March, September
Recommended planting time February to April, September to November
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Flowering time June to October
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Description

Persicaria polymorpha forms a large clump which does not sucker, 2m (7ft) in height, covered in midsummer with countless branched, pure white spikes of flowers.

 

This large perennial forms a powerful and thick stump, but does not sucker.  Upright and robust stems emerge from this stump in spring, carrying a large lanceolate, bright green foliage, forming a large loose bush. In summer, Persicaria polymorpha bears countless flowers in long and large corymbs, pure white with a strange ammonia-like scent.

 

Hardy to -20°C (1°F) and easy to grow, Persicaria polymorpha thrives in full sun or partial shade, it grows in rich, heavy, damp to moist soils. Plant it in the back of a border, in a lush and exotic garden alongside Gunnera, Astilboides tabularis, Chinese palm and Filipendulas.

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Persicarias or Knotweeds: planting, cultivation and maintenance
Family sheet
by Alexandra 12 min.
Persicarias or Knotweeds: planting, cultivation and maintenance
Read article

Persicaria polymorpha - Knotweed in pictures

Persicaria polymorpha - Knotweed (Flowering) Flowering
Persicaria polymorpha - Knotweed (Foliage) Foliage
Persicaria polymorpha - Knotweed (Plant habit) Plant habit

Flowering

Flower colour white
Flowering time June to October
Inflorescence Corymb
Fragrance slightly scented

Foliage

Foliage persistence Deciduous
Foliage colour light green

Plant habit

Height at maturity 2 m
Spread at maturity 1.20 m
Growth rate normal

Botanical data

Genus

Persicaria

Species

polymorpha

Family

Polygonaceae

Origin

Cultivar or hybrid

Product reference841202

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Planting and care

Grow Persicaria polymorpha in moist and clay soil, in full sun or partial shade. The plant has a slow growth and initially forms a strong stump during the first few years of cultivation, from which large stems will emerge.

Planting period

Best planting time March, September
Recommended planting time February to April, September to November

Intended location

Suitable for Meadow, Pond edge
Type of use Back of border
Hardiness Hardy down to -29°C (USDA zone 5) Show map
Ease of cultivation Amateur
Planting density 3 per m2
Exposure Sun, Partial shade
Soil pH Neutral
Soil type Clayey (heavy), Clayey-chalky (heavy and alkaline), Silty-loamy (rich and light)
Soil moisture Moist soil, Damp soil, Heavy, humus-rich, and damp

Care

Pruning No pruning necessary
Overwinter Can be left in the ground
4,5/5

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