Polygonum albinum (Knotweed) — Mat-forming, clump-forming or tall and upright

Overview

Polygonum albinum 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 albinum 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.

About

Polygonum albinum is a perennial in the knotweed family that can grow as a mat-forming ground cover, a clump, or as tall upright stems. It has deciduous, simple leaves that range from lance-shaped to heart-shaped and are often marked or take an autumn tint. Flowering occurs from July to September. Plants tolerate a wide range of soils, including heavy clay, and are suited to full sun or partial shade.

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 albinum is a perennial member of the Polygonaceae (knotweed) family that shows a wide range of habits: it may spread as a mat, form discrete clumps or produce taller, upright stems. The leaves are deciduous and typically lance- to heart-shaped, often bearing markings and turning a noticeable autumn tint before falling. Flowering takes place from July to September. Grow Polygonum albinum in full sun to partial shade on almost any soil, including heavy clay; it tolerates acid, neutral or alkaline pH. It prefers moist conditions and generally withstands damp ground but dislikes drought, so allow for consistent moisture during dry spells. The species is winter-hardy in UK gardens (H5–H7), so it will survive most frosts and exposed sites, and it suits any aspect. Use the mat-forming habit where ground cover is wanted, the clumping form at the front of mixed borders, and the taller form where vertical stems can provide summer structure. Its tolerance of exposed or sheltered positions and hardiness range make it flexible for urban beds, damp borders and margins where soil remains reasonably moist. Leaves commonly show markings and an autumn tint before dropping, which you can leave to provide seasonal colour before clearing.

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 albinum 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

Care notes

Pruning and caring for Polygonum albinum

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 albinum?

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 albinum?

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

What soil does Polygonum albinum need?

Polygonum albinum 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 albinum?

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 albinum hardy in the UK?

Polygonum albinum 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 albinum?

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

More in the Polygonum genus

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