Polygonum sachalinense

F. Schmidt

Giant knotweed, Sakhalin Knotweed, Sachaline

PolygonaceaeLeavesSeeds/NutsPotential hazards — see below
Caution — Parts of this plant may be toxic or require specific preparation. Verify with multiple sources before consuming.
Polygonum sachalinense
iNaturalist · cc-by-nc
(c) Oleksandr Shynder, some rights reserved (CC BY-NC)
Polygonum sachalinense
iNaturalist · cc-by-nc
(c) Oleksandr Shynder, some rights reserved (CC BY-NC)
Polygonum sachalinense
iNaturalist · cc-by-nc
(c) Oleksandr Shynder, some rights reserved (CC BY-NC)

What to Eat

Edible parts: Leaves, Seeds

Young spring shoots can be eaten raw or added to salads, or cooked as an asparagus substitute. They have an acid flavour, though in practice they more closely resemble a rhubarb substitute. Older stems and shoot tips can be cooked after peeling; they taste like a mild, lemon-tinged version of rhubarb and are considered superior in quality. The seed can be cooked, ground into a powder for use as a soup thickener and flavouring, or used as an extender in flour. The seed is quite small and fiddly to work with.

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.

Where to Find It

It is a temperate plant.

Asia, Britain, Europe, Japan, North America, USA,

Countries: Andorra, United Arab Emirates, Afghanistan, Antigua & Barbuda, Albania, Armenia, Austria, Azerbaijan, Bosnia & Herzegovina, Barbados, Bangladesh, Belgium, Bulgaria, Bahrain, Brunei, Bahamas, Bhutan, Belarus, Belize, Canada, Switzerland, China, Costa Rica, Cuba, Cyprus, Czechia, Germany, Denmark, Dominica, Dominican Republic, Estonia, Spain, Finland, France, United Kingdom, Grenada, Georgia, Greece, Guatemala, Honduras, Croatia, Haiti, Hungary, Indonesia, Ireland, Israel, India, Iraq, Iran, Iceland, Italy, Jamaica, Jordan, Japan, Kyrgyzstan, Cambodia, St Kitts & Nevis, North Korea, South Korea, Kuwait, Kazakhstan, Laos, Lebanon, St Lucia, Liechtenstein, Sri Lanka, Lithuania, Luxembourg, Latvia, Monaco, Moldova, Montenegro, North Macedonia, Myanmar, Mongolia, Malta, Maldives, Mexico, Malaysia, Nicaragua, Netherlands, Norway, Nepal, Oman, Panama, Philippines, Pakistan, Poland, Puerto Rico, Portugal, Qatar, Romania, Serbia, Russia, Saudi Arabia, Sweden, Singapore, Slovenia, Slovakia, San Marino, El Salvador, Syria, Thailand, Tajikistan, Timor-Leste, Turkmenistan, Turkey, Trinidad & Tobago, Taiwan, Ukraine, United States, Uzbekistan, St Vincent, Vietnam, Yemen

How to Identify

A vigorous perennial growing 3.6 m tall and 3 m wide at a fast rate, hardy to UK zone 5. Dioecious with male and female flowers on separate plants; flowering occurs July to October with seeds ripening August to October. Thrives in light sandy, medium loamy, and heavy clay soils across mildly acidic to mildly alkaline pH ranges. Adapts to semi-shade or full sun and prefers moist soil.

How to Grow

Succeeds in ordinary garden soil in sun or shade. Hardy to about -25°c. An extremely invasive plant, capable of sending up new shoots at a considerable distance from the main clump. Considered a pest in many areas, if grown in the garden it should be planted within a barrier to contain its roots. Plants seem to be immune to the predations of rabbits. Dioecious, male and female plants must be grown if seed is required.

Propagation: Sow seed in spring in a cold frame. Germination is usually straightforward. Once seedlings are large enough to handle, prick them out into individual pots and plant out during summer if they have grown sufficiently. If not, keep them in a cold frame over winter 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 their permanent positions. 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.

Medicinal Uses

None known

Other Uses

The plant is a potential source of biomass. Its vigorous growth also makes it a candidate for use as ground cover.

Wikipedia

Source ↗

A vigorous perennial growing 3.6 m tall and 3 m wide at a fast rate, hardy to UK zone 5. Dioecious with male and female flowers on separate plants; flowering occurs July to October with seeds ripening August to October. Thrives in light sandy, medium loamy, and heavy clay soils across mildly acidic to mildly alkaline pH ranges. Adapts to semi-shade or full sun and prefers moist soil.

Notes

There are about 50 Polygonum species.

Names & Synonyms
Reynoutria sachalinensis
References (6)
  • Duke, J.A., 1992, Handbook of Edible Weeds. CRC Press. p 154
  • Elias, T.S. & Dykeman P.A., 1990, Edible Wild Plants. A North American Field guide. Sterling, New York p 99
  • Facciola, S., 1998, Cornucopia 2: a Source Book of Edible Plants. Kampong Publications, p 186 (As Reynoutria sachalinensis)
  • C. J. Maximowicz, Mem. Acad. Imp. Sci. St.-Petersbourg Divers Savans 9:233. 1859 (Prim. fl. amur.)
  • Plants for a Future database, The Field, Penpol, Lostwithiel, Cornwall, PL22 0NG, UK. http://www.scs.leeds.ac.uk/pfaf/
  • Tanaka,

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