Lycopus americanus (American water-horehound)

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Lycopus americanus Muhl. ex W.P.C. Barton

American water-horehound

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Asteridae	A large class that encompasses asters
Order	Lamiales	Aromatic herbs and shrubs, including lavender, lilac, olive, jasmine, ash, teak, snapdragon, sesame, psyllium, garden sage, mint, basil, and rosemary
Family	Lamiaceae	Mint family
Genus	Lycopus	From the Greek lykos, “wolf,” and pous, “foot”
Species	americanus	American

About plant names...

American water-horehound is a North American native. It prefers lake and river shores, and wetland edges.

Plants: 12-36" (30-91 cm) tall, unbranched or sparingly branched, sometimes sprawling. The main stem is four-angled and ridged, and hairless or nearly so.

Leaves: Lower leaves are deeply lobed, and up to 3½" (8.9 cm) long × 1½" (3.8 cm) wide. Leaves are narrowly oval, narrowly oblong, or linear. They are opposite, becoming smaller near the top, and coarsely toothed. Upper leaf surfaces are typically hairless.

Flowers: In small clusters at leaf axils. Individual flowers are ⅛" (3.2 mm) in size, and white, with tiny purplish spots. They are tubular in shape, emerging in all directions from leaf axils.

Fruits: Nutlets are in groups of four, together forming a square shape. Each is ¹/₃₂-¹/₁₆" (1.2-1.7 mm) long.

Members of Lycopus, the water-horehounds, are notoriously hard to distinguish. They are also easily confused with some members of other genera. Here are some comparisons.

9/2/2017 · Rocky Ridge Trail, Beaver Brook Conservation Area, Hollis, New Hampshire
≈ 4½ × 6" (12 × 14 cm)

8/18/2010 · J. Harry Rich Woods, off Nod Rd., Groton, Massachusetts
≈ 5 × 8" (13 × 19 cm)

8/18/2010 · J. Harry Rich Woods, off Nod Rd., Groton, Massachusetts
≈ 7 × 8" (18 × 19 cm) ID is uncertain

	You are here Lycopus americanus	*Lycopus uniflorus*	*Lycopus virginicus*
Common Name	American water-horehound	northern bugleweed	Virginia water horehound
Plant	12-36" (30-91 cm) tall, unbranched or sparingly branched, sometimes sprawling. The main stem is four-angled and ridged, and *hairless or nearly so.*	4-20" (10-50 cm) tall, usually straight or with a few branches. Stems are four-angled and almost hairless.	15-36" (38-91 cm) tall, with an unbranched stem. It is erect, or sometimes leaning. Stems are roughly square in cross-section, and *covered with fine hairs* which may point outward or lie flat against the stem (appressed). These plants often (but not always) lack the thick tuberous roots of other water-horehounds.
Flowers	In small clusters at leaf axils. Individual flowers are ⅛" (3.2 mm) in size, and white, with tiny purplish spots. They are tubular in shape, emerging in all directions from leaf axils.	Flowers occur in dense clusters at leaf axils. They are tubular, reaching in every direction from the leaf axil, and about ⅛" (3.2 mm) around at the end.	Flowers appear in tight clusters at leaf axils. They are tubular in shape, and each is about ⅜" (1 cm) long × ⅛" (3.2 mm) in diameter. They emerge in all directions from the axil. Flowers are white, with a few pink spots.
Leaves	*Lower leaves are deeply lobed*, and up to 3½" (8.9 cm) long × 1½" (3.8 cm) wide. Leaves are narrowly oval, narrowly oblong, or linear. They are opposite, becoming smaller near the top, and coarsely toothed. Upper leaf surfaces are typically hairless.	Up to 3" (7.6 cm) long × 1" (2.5 cm) wide. They are hairless or nearly so, with 2-7 teeth on each side of the leaf. The leaves are opposite, and each pair are rotated 90° from the previous pair.	1-4½" (3-12 cm) × ⅜-1¾" (1-5 cm). Oval or lanceolate, unlobed, with coarsely toothed edges. The lowest teeth are a little below the mid-point of each leaf. *Leaves are more egg-shaped* than those other water-horehounds. Leaves are dark green or purple, and opposite. Leaves nearer the bottom have a short stalk, while those near the top are attached almost directly to the stem. Upper leaf surfaces are nearly hairless, while lower surfaces have a hairy central vein and may have fine hairs elsewhere.
Fruit	Nutlets are in groups of four, together forming a square shape. Each is ¹/₃₂-¹/₁₆" (1.2-1.7 mm) long.	Nutlets are ¹/₃₂-¹/₁₆" (1-2 mm), in groups of four.	Each flower is replaced by four small nutlets, packed in roughly the shape of a square. Nutlets are ¹/₃₂-¹/₁₆" (1.3-2 mm) × ~¹/₃₂" (0.7-1.3 mm).
Range/ Zones		USDA Zones: 4-8
Habitats	Lake and river shores, and wetland edges.	Wet areas such shores, swamps, marshes, wet meadows, and stream banks.	River banks, floodplains, wet meadows, clearings, and shores.
Type	Wild	Wild	Wild
Occurrence

	*Leonurus cardiaca*
Common Name	motherwort
Plant	24-39" (60-100 cm) high. The stems are square in cross-section. *Their preference for dryer habitats distinguishes them from water horehounds.*
Flowers	Between each pair of leaves, a tuft of small pink-purple flowers appear directly on the stem, becoming more closely spaced near the top
Leaves	Leaves are opposite. Pairs of leaves extend from the stem every inch or so, in alternating directions exactly at right angles to each other, looking almost unnaturally orderly. Leaves are dark green, and are 2-4" (5-10 cm) long. Younger leaves have *three pointed tips,* while older ones are further divided.
Fruit	Each flower becomes 4 reddish brown or brown nutlets. Each nutlet is 3-sided.
Range/ Zones
Habitats	Woodland borders, disturbed open woodlands, and partially shaded yard edges.
Type	Wild
Occurrence	Common