Hemp-nettle

Mint (Lamiaceae family):

Galeopsis tetrahit L.

EPPO code:

GAETE

Other names:

Bee nettle, dog nettle, flowering nettle

Species information

Lifecycle:

Annual.

Propagation:

Reproduces by seed.

Emergence:

Hemp-nettle is a very early germinating species.

Habitat:

It can be found throughout the province, but is most commonly found in cereal crops in central and northern Ontario.

Competitiveness:

The plant’s impact is greatest on cereal crops where significant yield losses have been observed. Due to its early germination pattern, hemp-nettle is often controlled by tillage or pre-plant herbicide applications.

Identification clues

Seedling

Cotyledons:

Orbicular with basal points (two small auricles pointing backwards) 5–15 mm long.

First leaves:

Oval to elongated, densely hairy with toothed margins and prominent veins.

Mature leaves:

Mature leaves have an opposite leaf orientation. They are oval with a “stretched out” tip, and hairy with toothed margins and prominent veins.

Mature plant

Stems:

Hemp-nettle’s stem is erect, branched, square and covered with coarse, downward- pointing hair.

Flowers:

Flowers appear in dense clusters in the leaf axils, and they have irregular-shaped, pinkish white to purple petals, which make them look somewhat like miniature snapdragon flowers.

Seeds:

Each flower has four, egg-shaped seeds located in the base of a tubular receptacle.

Roots:

Taproot with branched, lateral roots.

Often mistaken for

I know it's not Hairy galinsoga because hemp-nettle has cotyledons with basal points, a square stem and irregular- shaped, pinkish-white to purple flowers compared to the round stem of hairy galinsoga with its small, yellow and white flower head.