Persicaria alpina (All.) H. Gross.
alpine knotweed
A tall, clump-forming semi-evergreen perennial to 1.5 with large, willowherb-like lance-shaped fine green leaves which turn to brown-orange in august, and strong stems bearing plumes of small, airy, delicately fragrant creamy-white flowers which flower over a long period in summer, followed by pinkish-red seed heads in late summer. Suitable for the back of a flower border. Holds well without the need for staking
Synonyms
Aconogonon alpinumPolygonum alpinum
see morePersicaria alpina (All.) H. Gross.
Polygonum polymorphum
Persicaria polymorpha
Buy this plant
Size
Ultimate height
1.5–2.5 metresTime to ultimate height
2–5 yearsUltimate spread
1–1.5 metresGrowing conditions
Moisture
Moist but well–drained, Poorly–drainedpH
Acid, Alkaline, NeutralColour & scent
| Stem | Flower | Foliage | Fruit | |
| Spring | Green | |||
|---|---|---|---|---|
| Summer | Cream White | Green | Red | |
| Autumn | Green | |||
| Winter | Brown Orange |
Position
- Full sun
- Partial shade
Aspect
North–facing or West–facing or East–facing or South–facing
Exposure
Exposed or ShelteredDrought resistance
Yes Hardiness
H6Botanical details
- Family
- Polygonaceae
- Native to GB / Ireland
- No
- Foliage
- Semi evergreen
- Habit
- Clump forming
- Potentially harmful
- Contact with all parts may irritate skin, the sap may cause mild stomach upset if ingested. Wear gloves and other protective equipment when handling
- Genus
A genus of annual or clump-forming perennial plants with terminal or axillary inflorescences carried on upright stems. Flowers are small, pale-coloured usually white or pink. Seeds are borne in achenes
- Name status
Correct
- Plant range
- Eurasia
How to grow
Cultivation
Grow in any moist soil in full sun or partial shade. Substantial mounds of foliage steadily increase in size, needing space and careful siting
Propagation
Propagate by division in spring or autumn or propagate by seed in spring
Suggested planting locations and garden types
- City and courtyard gardens
- Cottage and informal garden
- Prairie planting
- Rock garden
- Gravel garden
- Low Maintenance
- Cut flowers
- Flower borders and beds
- Hedging and screens
- Wall side borders
Pruning
No pruning required. Cut back after flowering
Pests
Generally pest-free
Diseases
Generally disease-free
Get involved
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.