Polygonum weyrichii
(F. Schmidt ex Maxim.) Ronse Decr.
White Knotweed, Chinese knotweed
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Summary
Source: WikipediaA perennial plant growing to 1.5 m (5 ft) tall, hardy to UK zone 5. Flowers from July to September. Hermaphroditic and insect-pollinated. Adapts to light sandy, medium loamy, and heavy clay soils with mildly acid to basic pH. Tolerates semi-shade or full sun, prefers moist soil, and can withstand maritime exposure.
Description
A perennial plant growing to 1.5 m (5 ft) tall, hardy to UK zone 5. Flowers from July to September. Hermaphroditic and insect-pollinated. Adapts to light sandy, medium loamy, and heavy clay soils with mildly acid to basic pH. Tolerates semi-shade or full sun, prefers moist soil, and can withstand maritime exposure.
Edible Uses
Young shoots are eaten cooked. The seeds, though rather small and fiddly to work with, can be dried and ground into a powder for use with cereals in making bread, porridge, and similar foods.
Medicinal Uses
None known
Known Hazards
Although no specific mention has been made for this species, there have been reports that some members of this genus can cause photosensitivity in susceptible people. Many species also contain oxalic acid (the distinctive lemony flavour of sorrel) - whilst not toxic this substance can bind up other minerals making them unavailable to the body and leading to mineral deficiency. Having said that, a number of common foods such as sorrel and rhubarb contain oxalic acid and the leaves of most members of this genus are nutritious and beneficial to eat in moderate quantities. Cooking the leaves will reduce their content of oxalic acid. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition.
Distribution
It suits hardiness zones 4-8.
Where It Grows
Asia, Japan,
Cultivation
Succeeds in an ordinary garden soil but prefers a moisture retentive not too fertile soil in sun or part shade. Repays generous treatment. Plants seem to be immune to the predations of rabbits.
Propagation
Sow seed in spring in a cold frame; germination is usually free and easy. Once seedlings are large enough to handle, prick them out into individual pots and plant out during summer if they have reached sufficient size. If not, overwinter in a cold frame and plant out the following spring after the last expected frosts. Division can be done in spring or autumn. Larger divisions can go directly into permanent positions, but smaller divisions are better potted up and grown on in light shade in a cold frame until well established, then planted out in late spring or early summer.
Other Uses
None known
Notes
There are about 50 Polygonum species.
Synonyms
References (2)
- Mem. Acad. Imp. Sci. St.-Peersbourg Divers Savans 9:234. 1859 (Prim. fl. amur.) (As Polygonum weyrichii)
- Plants for a Future database, The Field, Penpol, Lostwithiel, Cornwall, PL22 0NG, UK. http://www.scs.leeds.ac.uk/pfaf/ (As Polygonum weyrichii)
