Ontario Weeds: Marsh hedge-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: Marsh hedge-nettle, Stachys palustris L.,

Other Names: épiaire des marais, Woundwort, stachyde des marais

Family: Mint Family (Labiatae)

General Description: Perennial, reproducing by seeds and by rhizomes.

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Photos and Pictures

Marsh hedge nettle (A - plant before flowering; B - 2 flowers in a whorl near the tip of a stem; C - coarse, brittle rhizomes).

Marsh hedge-nettle. A. Leafy shoot from the upturned end of a fleshy horizontal underground rhizome.

B. Tip of flowering stem.

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Stems & Roots: Stems erect, 20-100cm (8-40in.) high, simple or loosely branching, square in cross-section, pubescent on the sides as well as on the angles, arising from upturned ends of rhizomes; rhizomes creeping, whitish, often much-branched, occasionally with thickened, succulent, brittle sections; leaves opposite, stalkless or on petioles usually not over 3mm (1/8in.) long; the main leaves lanceolate to elliptic, 3.3-15cm (1¼-6in.) long and 1-4cm (2/5-1½in.) wide, hairy on both surfaces, and margins with somewhat rounded teeth.

Flowers & Fruit: Inflorescence 2.5-25cm (1-10in.) long, composed of whorls of flowers in axils of upper leaves and becoming spike-like towards the ends of branches (similar to Germander), each whorl usually with 6 flowers; calyx short-hairy, 6-9mm (¼-3/8in.) long, the 5 lobes about equal and narrowed to fine, almost hair-like points; corolla rose-purple, mottled with paler and darker tones, 11-16mm (½-¾in.) long, hairy, with the large 3-lobed lower lip longer than the 2-lobed upper lip; each flower producing 4 hard "seeds" or nutlets; these dark brown, 1.8-2.2mm (1/12in.) long x 1.2-1.8mm (1/20-1/15in.) broad. Flowers from June to September.

Habitat: Marsh hedge-nettle occurs as both naturalized and native species in Ontario. The weedy form usually occurs in dense patches in poorly drained areas of fields.

Similar Species: It is distinguished from most other plants with opposite leaves by its square stems, its thick, white, brittle rhizomes, and its spike-like inflorescence of rose-purple flowers; and from other members of the Mint Family, all of which also have square stems and opposite leaves, by its thick, brittle, whitish rhizomes, its leaves having petioles not more than 3mm (1/8in.) long, its distinctly hairy leaves, its inflorescence of mostly 6-flowered whorls and the corolla being distinctly 2-lipped.

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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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