Japanese Knotweed - Japanese Bamboo - Japanese Buckwheat
Donkey Rhubarb
Fallopia japonica - (Houtt.) Ronse Decr.
Syn: Reynoutria japonica
Polygonaceae (Buckwheat) Famil
y


Photo courtesy Mike Carter, Pensacola, Florida
 

Japanese Knotweed is one of the most invasive weeds in the world. In Asia it is regarded as having medicinal value, and as such was introduced to North America in the 1870s as an ornamental and forage plant, but its extracts were never put to test as a medicinal herb. It is difficult to exaggerate how aggressive this species can be, as it has been observed growing through two inches of concrete, and it will regenerate from the smallest section of root tissue. Control of Japanese knotweed is laborious and expensive. Its preferred habitat is floodplains (river or stream floodplains), forest edges, meadows and fields, and the shores of rivers and lakes.

The leaves are simple (i.e., lobed or unlobed but not separated into leaflets); placed alternate on the stem. The leaf blade is entire (no teeth and no lobes).

The flowers are radially symmetrical; five petals, sepals, or tepals in each flower. Fusion of sepals and petals form a small cup or tube; eight stamens. Flowers in August and September.

Fruit is a capsule that does not split open when ripe.

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