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Persicaria polystachya


Common name: Himalayan knotweed
Synonyms: Persicaria wallichii
Origin: Asia
Code of conduct: Annex I (consensus list)
Invasive status (ISEIA protocol): Watch list
Main ornemental function: Mixed border • Cover ground


Perennial plant, rhizomatous, up to 0,9 to 2 m tall, forming dense stands. The stems are relatively translucent, hollow except at the nodes, colour varies from green to red. Leaves are lanceolate to narrowly ovate, almost glabrous to densely pubescent on lowerside. The flower colour is cream to pink.


Vegetative reproduction by rhizomes. Sexual reproduction is uncertain in Belgium. It is difficult to confirm the existence of viable seeds.


In Belgium P. polystachya is found in riparian zones and wetlands. The plant thrives on moist nutrient-rich soils, in various light conditions. It is commonly used as an ornamental and is planted in gardens and public green areas.


Species classified B2 in Belgium. P. polystachya have similar impacts than other knotweeds, but is less widespread in Belgium and less documented in literature. P. polystachya grows rapidly, can locally form dense clones able to displace native vegetation. For more information about this species, click here


Do not plant, do not buy this species

Possible native alternatives

Main ornemental function

Mixed border
Cover ground

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