Ontario Weeds: Hemp-nettle

Table of Contents

1. Name
2. Other Names
3. Family
4. General Description
   • Photos and Pictures
5. Stems and Roots
6. Flowers and Fruit
7. Habitat
8. Similar Species
9. Related Links

Name: Hemp-nettle, Galeopsis tetrahit L.,

Other Names: ortie royale, Bee nettle, Dog nettle, Flowering nettle, chardonnet, galéopside à tige carrées

Family: Mint Family (Labiatae)

General Description: Annual, reproducing only by seed.

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Photos and Pictures

Hemp-nettle. A. Base of plant.

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Stems & Roots: Stems erect, 30-80cm (12-32in.) high, branched, square, usually swollen at the nodes, covered with rather harsh, straight, long, somewhat downward-pointing hair; leaves opposite (2 per node), ovate to elliptic with stretched-out tips, stalked, sparsely hairy, margins with rounded teeth, veins mostly ending in notches between the teeth.

Flowers & Fruit: Flowers in dense clusters in the axils of leaves near the ends of stems and branches; calyx short, tubular, 10-ribbed, ending in 5 equal, narrow, sharp, spine-like teeth about 5mm (1/5in.) long; these very spiny when mature; corolla pinkish to light purplish or whitish, often variegated, and usually with 2 yellow spots, 12-23mm (½-7/8in.) long, of 5 united petals, irregular, tubular, 2-lipped at the end, the upper lip 2-lobed, lower lip 3-lobed, each flower producing 4 egg-shaped nutlets ("seeds"), narrowed and somewhat triangular towards the basal end, about 3mm (1/8in.) long and grayish-brown. Flowers from mid-July to mid-August.

Habitat: Hemp-nettle occurs throughout Ontario, especially in central and northern areas, forming dense stands in grainfields and also present in seeded pastures, gardens, waste areas and along roadsides.

Similar Species: It is distinguished by being an annual with erect square stems covered with harsh downward-pointing hair frequently with a prominent swelling below each node, opposite leaves with stretched-out tips, leaf margins with rounded teeth, and dense clusters of pinkish or light purplish flowers with slender, sharp calyx lobes which become hard and very spiny at maturity.

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Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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