Knotweed, Japanese
LATIN: Reynoutria japonica Houtt.

Knotweed, Japanese
Family : Polygonaceae
Flowering Cévennes: 9 - 10 . Light: sunny. . Moisture: damp
Sample Cévenol GPS : 44°18.77' N 3°35.90' E
Status: not under threat in this region
Habitat: (view in new page) :Secondary : Banks of sand, gravel and river stones.

Renouée de Japon
Famille : Polygonaceae
Floraison Cévennes : 9 - 10 . Lumière: ensoleillé. . . Humidité: humide
Exemple Cévenol GPS : 44°18.77' N 3°35.90' E
Statut : pas menacé dans ce région
Habitat : (s'ouvrir nouvelle page) :Secondaire : Bancs de sable, de graviers et de galets.
Renouée de Japon
Reynoutria japonica
Knotweed, Japanese
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(des sources variées, pas inclus dans Coste) :

Cette grande plante vigoureuse a des tiges creuses érigées, rougeâtres, semblables à des cannes de bambou, de 1 à 3 m de haut. Rhizome/hémicryptophyte érigée : les tiges aériennes meurent l'hiver et seuls persistent des bourgeons souterrains et/ou au raz du sol.
Écologie : [Introduit] zones alluviales et les rives des cours d'eau, formant de larges fourrés denses. Aussi bords des routes, alentours des jardins, terrains abandonnés.
Répartition hors de France :

Knotweed, Japanese plant

(modified from Butcher, British Flora 1961):
NOTE: the French text is more complete and up-to-date

A large plant with stout, red, erect, annual stems 90-150 cm high, growing from a thick, creeping rootstock. Hollow stems with distinct raised nodes that give it the appearance of bamboo , though it is not closely related. While stems may reach a maximum height of 3-4 m each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement or are repeatedly cut down.
Ecology UK: (distribution according to flora) Native to Eastern Asia. In Europe the species is very successful and has been classified as an invasive species in several countries., including the UK


Carte (2021) grâce à Tela Botanica

Fleurs : blanches, petites, disposées en panicules à l'aisselle des feuilles ; 5 tépales persistantes, 8 étamines et 3 styles.
Floraison France : septembre-octobre

Flowers: 4 mm diam., cream or white, long stalked, in terminal and axillary panicles; perianth lobes 5, white, ovate, suberect; stamens 6-8, becoming longer than the lobes; styles 3, rather long; outer perianth winged in fruit.
Flowering UK: Mid Aug.-late Sept

Feuilles : alternes, inférieures largement ovales-triangulaires atteignent 15-20 cm de long et sont brusquement tronquées à la base.

Knotweed, Japanese leaf

Leaves: broadly ovate with a truncate base and acute apex, margin wavy, blade glabrous, veins reddish; ochrea fringed, much shorter than the internodes, glabrous. 7-14 cm long and 5-12 cm broad, with an entire margin.

Fruit : akène de 2-4 mm de long.

Knotweed, Japanese fruit

Fruit: Nut 4 x 2 mm, triquetrous with a broad wing, yellow.
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