''Reynoutria'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...

s in the family

Polygonaceae The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus ''Polygonum'', and was first used by Antoine Laurent de Jussieu in ...

. The genus is native to eastern China,

Eastern Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea ...

and the

Russian Far East The Russian Far East (russian: Дальний Восток России, r=Dal'niy Vostok Rossii, p=ˈdalʲnʲɪj vɐˈstok rɐˈsʲiɪ) is a region in Northeast Asia. It is the easternmost part of Russia and the Asian continent; and is admin ...

, although species have been introduced to Europe and North America. Members of the genus, including '' R. japonica'' (Japanese knotweed) and its hybrid with '' R. sachalinensis'', are highly invasive plants.

Description

Species placed in the genus ''Reynoutria'' are robust erect

perennial plant A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

s, growing from

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

s. They are usually

monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is ...

, with mostly bisexual flowers, but also some unisexual flowers. The

petal Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usuall ...

s of the flowers are dry and paperlike when mature. The fruits are

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not o ...

s with threefold sharp edges. The

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are forme ...

is in the form of a

panicle 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 panicle are of ...

. The flowers have separated triangular stigmas with fringes (fimbriate) borne on long divided styles.

Taxonomy

The genus ''Reynoutria'' was erected by

Maarten Houttuyn Maarten Houttuyn or Houttuijn (1720 – 2 May 1798) Latinised as Martinus Houttuyn, was a Dutch naturalist. Houttuyn was born in Hoorn, studied medicine in Leiden and moved to Amsterdam in 1753. He published many books on natural history, e.g. ...

in 1777 for the species ''R. japonica''. It was named in honour of Herr von Reynoutre who had been reported to have done a great deal of service to botany. As with many species in the family Polygonaceae, the taxonomic boundaries of ''Reynoutria'' have been much confused; in particular, it has been repeatedly merged with and separated from '' Fallopia''. A series of

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies have clarified relationships; ''Reynoutria'' is a well-supported

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

taxon. ''Reynoutria'' is placed in the tribe Polygoneae of the subfamily

Polygonoideae Polygonoideae is a subfamily of plants in the family Polygonaceae. It includes a number of plants that can be highly invasive, such as Japanese knotweed, ''Reynoutria japonica'', and its hybrid with '' R. sachalinensis'', ''R.'' × ''bohemica ...

. Within the tribe, it is most closely related to the genera '' Muehlenbeckia'' and ''Fallopia''

s.s. The ''Schutzstaffel'' (SS; also stylized as ''ᛋᛋ'' with Armanen runes; ; "Protection Squadron") was a major paramilitary organization under Adolf Hitler and the Nazi Party in Nazi Germany, and later throughout German-occupied Europe duri ...

, forming the so-called "RMF clade".

Species

Plants of the World Online Plants of the World Online (POWO) is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants by ...

recognized the following species: *'' Reynoutria ciliinervis'' (Nakai) Moldenke *''

Reynoutria japonica ''Reynoutria japonica'', synonyms ''Fallopia japonica'' and ''Polygonum cuspidatum'', is a species of herbaceous perennial plant in the knotweed and buckwheat family Polygonaceae. Common names include Japanese knotweed and Asian knotweed. It is ...

'' Houtt. – Asian knotweed, Japanese knotweed *'' Reynoutria multiflora'' (Thunb.) Moldenke – Chinese knotweed *''

Reynoutria sachalinensis ''Reynoutria sachalinensis'' (giant knotweed or Sakhalin knotweed Japanese オオイタドリ ''ooitadori'', Russian Горец сахалинский, Гречиха сахалинская; syns. ''Polygonum sachalinense'', ''Fallopia sachaline ...

'' (F.Schmidt) Nakai – giant knotweed, Sakhalin knotweed * ''Reynoutria'' × ''bohemica'' Chrtek & Chrtková 'R. japonica'' × ''R. sachalinensis''– Bohemian knotweed

Invasive potential

All members of the RMF clade appear to have the potential to become invasive, in some cases via vigorous hybrids. ''

'' is highly invasive throughout Europe and North America. The hybrid between ''R. japonica'' and '' R. sachalinensis'', ''R.'' × ''bohemica'', is also invasive, particularly in North America. ''R. japonica'' hybridizes with the New Zealand '' Muehlenbeckia australis''. (The related '' M. complexa'' has established populations in southern parts of Britain and in the Channel Islands.)

References

{{Taxonbar, from=Q2714294 Polygonoideae Polygonaceae genera