Wireweed (Polygonum heterophyllum)
Common Names
Also known as: Hogweed, Knotweed, Prostrate Knotweed.
Description
Wireweed is a low-growing, spreading herb that can be annual or perennial. Its slender, wiry stems can grow up to 1 metre long and form dense mats. The small oval leaves (5-15 mm) have a silvery sheath at the base. Clusters of tiny pink-tinged flowers (2-3 mm) appear in leaf axils, with each flower having five lobes and three styles. The fruit is small, triangular, and enclosed in the withered flower.
Native to Europe, Wireweed is commonly found in pastures, roadsides, and waste areas. It flowers in autumn and spring.
Stem and Leaves
- Stems are wiry, grooved, hairless, and reddish.
- Leaves are spear-shaped with pointed tips and a short stalk.
- A thin sheath surrounds the base of each leaf and stem.
Flowers and Fruit
- Flowers grow in clusters of 1-5 in leaf axils.
- Fruit is a small, triangular nut (2-2.5 mm), brown to reddish-black with fine dots and streaks.
Reproduction and Dispersal
Wireweed spreads by seed.
Similar Species
- Ribwort (Plantago lanceolata) – Similar as a seedling but has longer cotyledons, a hairy first leaf, and no sheath at the leaf base.
- Buck’s Horn Plantain (Plantago coronopus) – Similar as a seedling but develops lobed leaves and lacks a sheath at the leaf base.