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

Overview

Polygonum equisetiforme 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 1.0 m tall. Polygonum equisetiforme 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. It is native to Portugal Continental.

About

Polygonum equisetiforme is a perennial knotweed that can form mats, clumps or grow upright to about 1.0 m. It has deciduous, simple leaves that range from lance-shaped to heart-shaped and are often marked or take on autumn tints. Flowering occurs July to September. It suits a wide range of sites, including heavy clay and damp ground.

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 equisetiforme belongs to the Polygonaceae and originates from Continental Portugal. Its growth habit is variable — plants may spread as a mat, form compact clumps or reach about 1.0 m when upright — and the foliage is deciduous, often showing markings or autumn colour as the season advances. Flowering runs from July to September. Plant in full sun to partial shade on almost any soil, including heavy clay; it accepts acid, neutral or alkaline pH. It prefers moist conditions and most plants tolerate damp ground but dislike drought, so avoid sites that dry out in summer. The hardiness rating H5–H7 (hardy to fully hardy) means it will withstand the normal range of UK winter conditions across most regions, whether in exposed or sheltered positions and on any aspect. Use mat-forming forms to hold soil on damp banks or as a ground cover at the rear of moisture-retentive borders; upright forms can provide a herbaceous spike to mixed beds and borders. Expect the leaves to take on autumn tints as growth dies back, which can help mark the end of the season in a damp border.

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 equisetiforme 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: 1.0 m
Native to: Portugal Continental

Care notes

Pruning and caring for Polygonum equisetiforme

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 equisetiforme?

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 equisetiforme?

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

What soil does Polygonum equisetiforme need?

Polygonum equisetiforme 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 equisetiforme?

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 equisetiforme grow?

Polygonum equisetiforme reaches a height of 1.0 m.

Is Polygonum equisetiforme hardy in the UK?

Polygonum equisetiforme 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 equisetiforme?

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

More in the Polygonum genus

Browse all Polygonum →