 |
(a) Japanese knotweed leaf and petiole. Leaf: mid-green, shield-shaped (pointed tip with a straight edge along the top). Leaves can vary in size. mature knotweed plants, often partially visible above ground. The most regenerative part of the plant. Thick, fibrous roots and rhizomes grow from the crowns. Petiole (leaf stem): distinctive zig-zag, due to leaves growing alternately along the stem. Often pink/purple in colour. |
 |
(b) Japanese knotweed stems and exposed crown (glove indicates scale). Stem: bamboo-like, hollow, jointed. Green, often with a pink/purple speckle. Crown: a knotty mass in the ground at the foot of stems on mature knotweed plants, often partially visible above ground. The most regenerative part of the plant. Thick, fibrous roots and rhizomes grow from the crowns. |
 |
(c) Japanese knotweed rhizome (cross-section). Rhizome: an underground stem system that can spread several metres in any direction. In mature plants, rhizomes grow from the crowns with many pushing up to the surface as new shoots. Internally rhizome is orange, rather like a carrot, though can be bleached white when very young. Wispy, fibrous roots grow from the surface of mature rhizomes. |
 |
(d) Japanese knotweed flower. Flower: small, white, 5-petalled, appearing in clusters in late August. Persist until October/November. |
