Polygonum affine (Himalayan bistort, fleece flower) — Mat-forming, clump-forming or tall and upright

Overview

Polygonum affine 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. Polygonum affine 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 groundcover, borders and rock gardens. It is native to Himalayas.

About

Polygonum affine is a perennial from the Himalayas that can form low mats, clumps or produce taller upright flowering stems. Leaves are deciduous, lance-shaped to heart-shaped and are often marked or take on autumn tints. It flowers July to September. It prefers full sun to partial shade and suits moist soils, including heavy clay, but dislikes drought.

Wikipedia contributors, CC BY-SA 4.0 — Bistorta affinis

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

Polygonum affine belongs to the family Polygonaceae and originates in the Himalayan region. Its habit is variable: it can spread as a mat-forming ground cover, grow in clumps or send up taller, erect flowering shoots, and the foliage tends to show markings or autumn colour before it dies back. Flowering is concentrated from July to September. Grow it in full sun to partial shade on almost any soil, including heavy clay; pH can be acid, neutral or alkaline. The species tolerates damp ground and dislikes drought, so choose a moisture-retentive site or water in prolonged dry spells. It tolerates exposed or sheltered sites and suits most of the UK, being classed H5–H7 (hardy to fully hardy). Use Polygonum affine as a ground cover between stepping stones, at the front of mixed borders or on suitable rock garden slopes where a mat-forming habit is wanted. It will fill gaps and help suppress shallow weeds if planted close together; for taller forms, allow room for flowering stems among herbaceous perennials. Position plants where moisture is more reliable rather than in a dry, hot bank.

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 affine 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
Suggested uses: Groundcover, Borders, Rock gardens
Native to: Himalayas

Care notes

Pruning and caring for Polygonum affine

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 affine?

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 affine?

Polygonum affine prefers full sun to partial shade. It suits exposed or sheltered positions.

What soil does Polygonum affine need?

Polygonum affine 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 affine?

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.

Is Polygonum affine hardy in the UK?

Polygonum affine 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 affine?

Divide in spring or autumn - most divide very easily. Basal cuttings root readily in spring.

More in the Polygonum genus

Browse all Polygonum →