Polygonum polystachyum - Himalayan Knotweed

Family:	Polygonaceae
Habit:	Perennial
Height:	1.8
Width:	1.5
Synonyms:	Persicaria polystachya. (Wallich.)Gross.
Range:	E. Asia - Himalayas. Occasionally naturalized in Britain, it is common in S.W. England[17].

Polygonum polystachyum (Himalayan Knotweed) is a Perennial which grows to a height of 1.8m and a width of 1.5m . It has a fast growth rate. It has a hardness rating of 6.
Himalayan Knotweed will flower in January to March. the seeds ripen from March to April
The flowers from this plant are hermaphrodite (has both male and female organs) and they are pollinated by

Soil Information

Himalayan Knotweed will grow in light (sandy),medium (loamy),hard (clay) soil. It is not necessary for the soil to be well drained.
The soil prefers the following PH / acid levels :
- pH of less than 6, Acidic soils
- pH between 6 and 8, Neutral soils
- pH greater than 8, Basic soils
Himalayan Knotweed prefers moist soils

Ideal Planting Locations

Himalayan Knotweed can grow in semi or areas with no shade.

Forests, shrubberies and open slopes, often gregarious, 2000 - 4000m from Afghanistan to S.W. China[51].

Planting places suited to this plant described below.

• Grows within a woodland garden
• Works within dappled Shade
• Grows in a shady edge
• Can spread to cover ground and will out compete weeds

Cultivation Details

Succeeds in an ordinary garden soil[1] but prefers a moisture retentive not too fertile soil in sun or part shade[200]. Repays generous treatment[1]. A vigorously spreading plant, it is only really suitable for large areas of ground[233]. Plants are easily mistaken for P. campanulatum[51]. Plants seem to be immune to the predations of rabbits[233].

Edible Uses*

* See disclaimer
Edible Rating: 2/5
Leaves - cooked[51]. Seed - raw or cooked. It is rather small and fiddly to utilize.

• Leaves -
• Seed - includes nuts, cereals, peas and beans.
• Stem - this often intergrades into leaves.

Medicinal Uses*

* See disclaimer
Medicinal Rating: 0/5
None known

Propagation

Seed - sow spring in a cold frame. Germination is usually free and easy. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in the summer if they have reached sufficient size. If not, overwinter them in a cold frame and plant them out the following spring after the last expected frosts. Division in spring or autumn. Very easy, larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.

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[238].

Other Uses

Plants are very vigorous and can be grown for ground cover, succeeding even on the verges of streams[208]. They are best spaced about 1.2 metres apart each way[208].

• Ground cover - Usually low growing plants that can be grown with other plants, especially shrubs and trees, to prevent the growth of weeds.

Cultivars

no recorded cultivars

References

Flowers of the Himalayas.
Polunin. O. and Stainton. A.
Author: Polunin. O. and Stainton. A.
Rating:
Publisher : A very readable and good pocket guide (if you have a very large pocket!) to many of the wild plants in the Himalayas. Gives many examples of plant uses.
Date of Publication : 1984

The New RHS Dictionary of Gardening. 1992.
Huxley. A.
Author: Huxley. A.
Rating:
Publisher : Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
Date of Publication : 1992

Flora of China

Author:
Rating: http://flora.huh.harvard.edu/china/
Publisher : On-line version of the Flora - an excellent resource giving basic info on habitat and some uses.
Date of Publication : 1994

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