knotweed

Any of various low-growing or shrubby plants of the family Polyganaceae, having jointed stems and small flowers.

A plant of one of the species of knapweed or knobweed, Centaurea nigra, C. Cyanus, and C. Scabiosa: so called from the knot-like heads.

A plant of the genus Polygonum, which includes the doorweed, the smartweeds and water-pepper, the prince’s-feather, etc.; knotgrass or jointweed: so called from the knotty stem.

See knotgrass.

Any of several plants of the genus Polygonum, with jointed stems and inconspicuous flowers