This broadleaf weed is considered to be highly competitive with crops for soil nutrients and moisture. It can also interfere with harvesting making it critical to identify and control early in the season. Hemp-nettle is an annual, seed-propagated weed with taproot, reaching up to 40 cm in height.
The cotyledon of Galeopsis tetrahit is smooth edged, oval-stemmed with two lobes at the base and has a rounded tip.
Stems, when cut in cross section, are square in shape and hairy. The hairs are bristle-like and can penetrate the skin when handling. Leaves are long and oval with soft hairs growing on both sides, and have swollen nodes below the leaves. Flowering period occurs from July to October, resulting typically in white flowers; however, it is possible to have pink or purple flowers, growing as dense whorls.
Optimal growth conditions
This plant prefers a cool damp habitat, such as fresh loams and sandy soils with high nutrient (nitrogen) content. This common weed is typically found in cultivated fields, along roadsides and waste places.