Lycopus americanus Muhl. - Common Water Horehound


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Lycopus americanus - (image 1 of 4)



Family: Lamiaceae


Marsh, Calcareous fens, ditches.


Asclepias incarnata, Calamagrostis canadensis, Carex stricta, Thelypteris palustris, Eupatorium perfoliatum, Galium obtusum, Iris virginica, Scirpus pungens, Spartina pectinata, Typha latifolia, Verbena hastata.


All of continental US except NV.


Herbaceous rhizomatous perennial. to 2' high. Leaves opposite, to 3" long, laceolate, glabrous or glabrate above or with appressed hair along the midrib, distinctly petiolate; lower and medium leaves pinnately incised. Stems 4-sided. Flowers tiny, tubular, white, in clusters in the axils of the leaves; calyx lobes attenuate to long subulate, with a prominent midvein, conspicuously surpassing the nutlets.


Flowers early July to late September.

Wetland indicator: Obligate

At first glance could be mistaken for Mentha arvensis.  


Niering, W. A. 1979. The Audubon society field guide to North American wildflowers: eastern region.
Knopf/Random House, New York.

Swink, F. and G. Wilhelm. 1994. Plants of the Chicago Region.
Indiana Academy of Science. The Morton Arboretum. Lisle, Illinois.


USDA, NRCS. 2002.
The PLANTS Database, Version 3.5 (
National Plant Data Center, Baton Rouge, LA 70874-4490 USA.




 Michael Hough 2005