Polygonum rigidum
Family: Polygonaceae
What it is like
Polygonum rigidum is a ANNUAL growing to 0.5 m (1ft 8in). It is in flower from June to August, and the seeds ripen from July to September. The species is hermaphrodite (has both male and female organs). Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.
Height (m): 0.5
Where it is found
Near fields or roadsides, shaded grassy places in valleys at elevations of 400 - 2500 metres in Gansu, Hebei, Heilongjiang, Jilin, Liaoning, Nei Mongol, Shaanxi and Shanxi Provinces.
E. Asia - China, Mongolia, Russia.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 1
Leaves and young shoot tips - raw or cooked. An emergency food, used when all else fails. Seed - raw or cooked. It is rather small and fiddly to utilize.
Seed: includes nuts, cereals, peas and beans.
Medicine
Rating: 0
Other
Rating:
How it is grown
We have very little information on this species and do not know if it is hardy in Britain, though judging by its native range it should succeed outdoors in many parts of the country. The following notes are based on the general needs of the genus. 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.
Propagating it: 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.
Best place to grow: Cultivated Beds;
Habit: Annual
Hardiness:
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Moist
Things to keep in mind
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.