''Reynoutria sachalinensis'', the giant knotweed or Sakhalin knotweed, (syns. ''Polygonum sachalinense'', ''Fallopia sachalinensis'') is a species of '' Fallopia'' native to northeastern Asia in northern Japan ( Hokkaidō,

Honshū , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the seventh-largest island in the world, and the second-most populous after the Indonesian ...

) and the far east of Russia ( Sakhalin and the southern Kurile Islands). ''Reynoutria sachalinensis'' is a

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of ...

perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...

growing to tall, with strong, extensively spreading

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

s forming large

clonal colonies A clonal colony or genet is a group of genetically identical individuals, such as plants, fungi, or bacteria, that have grown in a given location, all originating vegetatively, not sexually, from a single ancestor. In plants, an individual in ...

. The

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

are some of the largest in the family, up to long and broad, nearly heart-shaped, with a somewhat wavy, crenate margin. The

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s are small, produced on short, dense

panicle In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...

s up to long in late summer or early autumn; it is gynodioecious, with male and female (male sterile) flowers on separate plants. The species is closely related to the Japanese knotweed, '' Reynoutria japonica'', and can be distinguished from it by its larger size, and in its leaves having a heart-shaped (not straight) base and a crenate margin. ''Reynoutria sachalinensis'' has a

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

count of 2n=44.Flora of NW Europe
''Fallopia sachalinensis''
/ref>Huxley, A., ed. (1992). ''New RHS Dictionary of Gardening''. Macmillan .

Cultivation and uses

The shoots are tender and edible. It was introduced to Europe and grown in many botanic gardens. It came prominently into notice about 1893, when a

drought A drought is a period of drier-than-normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, ...

in western Europe caused a decided shortage in forage for cattle. This plant was little affected, and since its tender shoots and leaves were eaten by stock, the plant was widely grown experimentally as a forage crop. It has proved less useful than was predicted, and its deliberate cultivation has been almost entirely abandoned.'' New International Encyclopedia''. Yale University Press, 1926. It has, however, like ''F. japonica'', proved to be an invasive weed in several areas. It has hybridised with ''Reynoutria japonica'' in cultivation; the hybrid, '' Reynoutria × bohemica'' (Chrtek & Chrtková) J.P.Bailey, is frequently found in the British Isles and elsewhere.Japanese Knotweed Alliance
''Fallopia'' hybrids
Extracts of this plant can be used as plant protectants for certain fungal and bacterial diseases. Rhizome of ''R. sachalinensis'' is the source of lactoperoxidase peroxidation cycle substrates, which can act as activators and inhibitors of the antimicrobial properties of that system. The species has been cultivated as an energy crop for

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

production, particularly in Germany in its commercial variety 'Igniscum', and it has shown a high productivity even in Northern latitudes, reaching a dry matter yield from , annually.

References

{{Taxonbar, from1=Q28922301, from2=Q2210394 Polygonoideae Flora of Japan Plants described in 1859 Edible plants Forages Stem vegetables Flora of the Russian Far East