Japanese knotweed

Family: Polygonaceae
Scientific name: Fallopia japonica
Description: Plant Form: Thicket-forming perennial herb. Size: Up to 3 m tall. Stem: Robust, hollow, with conspicuously ring-like nodes, often reddish, dying back for winter. Often slightly zig-zagging. Leaves: Alternate, undivided, often more or less in one plane along the branch, broadly egg- to heart-shaped with drawn-out tip, up to 15 cm long, hairless. Flowers: Tiny, greenish to off-white, numerous, in long, thin groups at the leaf joins. Fruit and Seeds: Nutlets 2-4 mm long, dark brown to black, dispersed with three wings. Habitat: Gardens, streams, rivers, ditches. Distinguishing Features: Generally has smaller leaves and flower petals than other species in the genus Fallopia.

Example images for this weed