E-Flora BC: Electronic Atlas of the Flora of British Columbia

Lycopus americanus Muhl. ex W.P.C. Barton
cut-leaved water horehound (American water horehound)
Lamiaceae (Mint family)

Introduction to Vascular Plants

© Liz Watkinson  Email the photographer   (Photo ID #11798)

E-Flora BC Static Map
Distribution of Lycopus americanus
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Species Information

Perennial herb from rhizome, without tubers; stems erect, 20-80 cm tall, slender, simple or branched, 4-angled, generally glabrous but nodes short-hairy.
Opposite, oblong to lanceolate, 3-8 cm long, 1-3.5 cm wide, tips pointed, bases tapering to a short stalk, margins coarsely, irregularly and deeply toothed or cleft, lower teeth larger; uppermost leaves shallowly toothed to entire.
Inflorescence of many head-like, axillary flower clusters; corollas tubular, 4-lobed, white, 2-3 mm long, about the length of calyces; calyx teeth 5, awl-like, short-awned.
Nutlets, 4 clustered together, 1-1.5 mm long, 0.8-1.2 mm wide, 3-angled, corky-thickened on edges, smooth and broadly rounded at the top.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Early Summer
Fruit/Seed characteristics:
Colour: Brown
Present from Summer to Fall
Source:  The USDA

Habitat / Range

Lake and stream margins and moist forest edges in the lowland and montane zones; frequent in C and S BC; E to NF and S to CA and FL.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Lycopus americanus

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 380 1030 1620
Slope Gradient (%) 0 4 28
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
28 36 52
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
4 6 8
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: CDF(3), CWH(10), ESSF(1), ICH(2), SBPS(1), SBS(2), SWB(1)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is cool temperate & cool mesothermal.

Synonyms and Alternate Names

Lycopus americanus var. longii Benner
Lycopus americanus var. scabrifolius Fern.
Lycopus sinuatus Ell.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References