Overview
Polygonum amplexicaule is a mat-forming, clump-forming or tall and upright perennial in the genus Polygonum, part of the Polygonaceae family, with deciduous; simple, lance-shaped to heart-shaped, often marked or autumn-tinted foliage. It typically grows around 1.2 metres tall. Polygonum amplexicaule grows best in full sun to partial shade, and tolerates almost any soil and including heavy clay soils and acid and neutral or alkaline pH. Its UK hardiness is rated H5-H7. Suggested uses include borders, wildflower gardens and damp areas. It is native to China, Himalayas and Pakistan.
About
Polygonum amplexicaule is a perennial in the buckwheat family that tolerates moist, even damp, ground and grows to about 1.2 metres. Forms range from mat-forming or clump-forming to taller, upright plants. Leaves are deciduous, simple and lance- to heart-shaped, often marked or taking on autumn tints. It flowers in the UK from July to September.
Wikipedia contributors, CC BY-SA 4.0 — Bistorta amplexicaulis
About the genus
Polygonum is a genus of about 130 species of flowering plants in the buckwheat and knotweed family Polygonaceae. Common names include knotweed and knotgrass. In the Middle English glossary of herbs Alphita, it was known as ars-smerte.
Wikipedia contributors, "Polygonum", CC BY-SA 4.0 — Polygonum
In the garden
Native to China, the Himalayas and Pakistan, Polygonum amplexicaule belongs to the Polygonaceae and occupies a range of garden roles where soil remains reliably damp. Plants typically reach around 1.2 metres and can appear as low mats, compact clumps or taller upright clumps depending on the form chosen; foliage is simple and deciduous, usually lance- to heart-shaped and often showing marks or autumn colour. Position in full sun to partial shade, in almost any soil including heavy clay, and you will avoid most problems; the species tolerates acid, neutral and alkaline pH. It prefers moist conditions and most forms dislike drought, so aim for a site that remains damp rather than baked dry. Aspect and exposure are not critical, and the plants are rated H5–H7 for UK hardiness (from hardy to fully hardy). Use red bistort in mixed borders, wildflower or meadow-style plantings and damp garden corners where it can spread to form clumps. Space plants to suit the habit you want—closer for a mat-forming effect, wider for upright clumps—and expect summer flowering from July to September. Leaves often develop clear autumn tints before they are lost, giving a useful seasonal change after flowering.
Growing conditions
Best soil and position for Polygonum
- Sunlight
- Full sun to partial shade
- Soil type
- Almost any soil, including heavy clay
- Soil pH
- Acid, neutral or alkaline
- Soil moisture
- Moist; most tolerate damp ground and dislike drought
- Aspect
- Any
- Exposure
- Exposed or sheltered
- UK hardiness
- H5-H7
Plant details
Polygonum amplexicaule size, habit and characteristics
- Plant type
- Perennial
- Habit
- Mat-forming, clump-forming or tall and upright
- Foliage
- Deciduous; simple, lance-shaped to heart-shaped, often marked or autumn-tinted
- Height
- 1.2 metres
- Suggested uses
- borders, wildflower gardens, damp areas
- Native to
- China, Himalayas, Pakistan
Care notes
Pruning and caring for Polygonum amplexicaule
- Cultivation
- Undemanding to the point of needing restraint rather than encouragement. Give reliable moisture and they flower for months. Vigour is the main consideration: check the spread of any given species before planting, since the running kinds colonise fast and are difficult to remove once established, while the clump-forming ones are well behaved. Note that most garden knotweeds are now classified under Persicaria.
- Pruning
- Cut back to the base in late autumn, or leave the dried spikes standing for winter interest and clear in early spring. Shear mat-forming kinds after the first flush to tidy them.
- Propagation
- Divide in spring or autumn - most divide very easily. Basal cuttings root readily in spring.
- Pest resistance
- Slugs graze new growth; otherwise notably trouble-free.
- Disease resistance
- Healthy and robust. Powdery mildew occurs on plants that dry out.
Frequently asked questions
How do I grow Polygonum amplexicaule?
Undemanding to the point of needing restraint rather than encouragement. Give reliable moisture and they flower for months. Vigour is the main consideration: check the spread of any given species before planting, since the running kinds colonise fast and are difficult to remove once established, while the clump-forming ones are well behaved. Note that most garden knotweeds are now classified under Persicaria.
Where is the best place to plant Polygonum amplexicaule?
Polygonum amplexicaule prefers full sun to partial shade. It suits exposed or sheltered positions.
What soil does Polygonum amplexicaule need?
Polygonum amplexicaule grows best in almost any soil and including heavy clay soil. It prefers acid and neutral or alkaline soil. Aim for soil that stays moist; most tolerate damp ground and dislike drought.
How do I prune Polygonum amplexicaule?
Cut back to the base in late autumn, or leave the dried spikes standing for winter interest and clear in early spring. Shear mat-forming kinds after the first flush to tidy them.
How big does Polygonum amplexicaule grow?
Polygonum amplexicaule reaches a height of 1.2 metres.
Is Polygonum amplexicaule hardy in the UK?
Polygonum amplexicaule has an RHS hardiness rating of H5, meaning it is hardy in most of the UK, tolerating -15 to -10°C.
How do I propagate Polygonum amplexicaule?
Divide in spring or autumn - most divide very easily. Basal cuttings root readily in spring.
More in the Polygonum genus
- Polygonum affineHimalayan bistort, fleece flower
- Polygonum affine 'Superbum'Knotweed
- Polygonum albinumKnotweed
- Polygonum amplexicaule 'Arun Gem'Red Bistort
- Polygonum amplexicaule 'Atrosanguineum'Red Bistort
- Polygonum amplexicaule 'Firetail'Knotweed
- Polygonum amplexicaule 'Inverleith'Knotweed
- Polygonum amplexicaule oxyphyllum of gardensKnotweed
