Not the plant you're looking for? Search over 300,000 plants
Herbaceous PerennialSynonym

Persicaria alpina (All.) H. Gross.
  • RHS AGM

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
Polygonum alpinum
Persicaria alpina (All.) H. Gross.
see morePolygonum polymorphum
Persicaria polymorpha
Buy this plant
Size
Ultimate height
1.5–2.5 metres
Time to ultimate height
2–5 years
Ultimate spread
1–1.5 metres
Growing conditions
Clay
Loam
Moisture
Moist but well–drained, Poorly–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
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 Sheltered
Drought resistance
Yes
Hardiness
H6
Botanical details
Family
Polygonaceae
Native to the UK
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
Name status

Correct

Plant range
Himalaya

Advertise here

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

My Garden

Your free RHS gardening coach

Keep track of your plants with reminders & care tips – all to help you grow successfully

My plants
My calendar

My plants

My calendar

My ideas
Manage membership

My ideas

My advice

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.