Overview
Polygonum affine 'Superbum' 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 'Superbum' 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 'Superbum' is a perennial knotweed notable for its variable habit, forming mats, clumps or sometimes growing more upright. Leaves are deciduous, simple and range from lance-shaped to heart-shaped, often showing markings or an autumn tint. It flowers from July to September and prefers full sun to partial shade. The plant tolerates almost any soil including heavy clay, favours moist conditions and 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 'Superbum' is a perennial member of the Polygonaceae, native to the Himalayas, that can present as a low mat, a denser clump or a taller upright form. Its leaves are deciduous, simple in shape and often marked or flushed in autumn, while flowering occurs from July to September. Plant it in full sun to partial shade on almost any soil type, including heavy clay; soil pH is not critical and it tolerates acid, neutral or alkaline ground. The key cultural point is soil moisture: most plants of this species perform where the soil remains reliably moist, and they dislike drought, so avoid planting in consistently dry, free-draining spots. It suits both exposed and sheltered positions and any aspect. In British hardiness terms it is rated H5–H7 (hardy to fully hardy), so it will withstand typical UK winters across most regions. Use Polygonum affine 'Superbum' as a ground cover, in mixed borders or on rock garden slopes where moisture holds. It fills gaps at the front of borders or beneath taller perennials and can help knit together damp patches. Leaves often develop a noticeable autumn tint, providing a seasonally distinct look as flowering finishes.
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 'Superbum' 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 'Superbum'
- 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 'Superbum'?
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 'Superbum'?
Polygonum affine 'Superbum' prefers full sun to partial shade. It suits exposed or sheltered positions.
What soil does Polygonum affine 'Superbum' need?
Polygonum affine 'Superbum' 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 'Superbum'?
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 'Superbum' hardy in the UK?
Polygonum affine 'Superbum' 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 'Superbum'?
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 albinumKnotweed
- Polygonum amplexicaulered bistort, mountain fleece
- Polygonum amplexicaule 'Arun Gem'Red Bistort
- Polygonum amplexicaule 'Atrosanguineum'Red Bistort
- Polygonum amplexicaule 'Firetail'Knotweed
- Polygonum amplexicaule 'Inverleith'Knotweed
- Polygonum amplexicaule oxyphyllum of gardensKnotweed
