Ontario Weeds: Hemp-nettle

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  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.

Photos and Pictures

Hemp-nettle.

Hemp-nettle. A. Base of plant.

Hemp-nettle. A. Base of plant.


B. Portion of stem with 2 flowering branches.

B. Portion of stem with 2 flowering branches.

C. Flower.

C. Flower.

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.

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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