American Bugleweed
Lycopus americanus
Mint family (Lamiaceae)

Description: This perennial plant is about 1-3' tall; it is usually unbranched, otherwise branching sparingly. The green or reddish central stem is four-angled and ridged; it may be hairless or slightly pubescent. This plant has a tendency to sprawl in the absence of supportive vegetation. The opposite leaves are spaced somewhat widely along the stems; they are sessile or short-petioled. The leaf blades are up to 3" long and " across; they are lanceolate, ovate-lanceolate, or elliptic-lanceolate in shape. The lower leaves are narrowly lobed or pinnatifid toward their bases, while the upper leaves are coarsely dentate all along their margins. The leaves are hairless, except for a few hairs along the central veins of their undersides.

Dense axillary whorls of white flowers occur where pairs of middle to upper leaves join the stem. Individual flowers are about 1/8" (2-3 mm.) in length. Each flower has a white short-tubular corolla with 4 spreading lobes, a light green calyx with 5 teeth, 2 exerted stamens, and a pistil. The calyx teeth are narrowly triangular and about twice as long as they are across. The corolla is only a little longer than the teeth of the calyx. The blooming period occurs from mid-summer to fall, lasting about 2 months. Neither the foliage nor the flowers have any noticeable fragrance. Afterwards, the flowers are replaced by nutlets in groups of 4 that are shorter than the calyx. These nutlets are broad and flat at the top, becoming rounded and more narrow along 3 angles toward the bottom; they have smooth surfaces. The root system is rhizomatous, but lacks tubers. Colonies of clonal plants are often formed from the rhizomes.

Cultivation: The preference is partial to full sunlight and wet to moist conditions. This plant normally grows in flood-prone areas where the soil contains loam, silt, or clay.

Range & Habitat: The native American Bugleweed is a common plant that occurs in all counties of Illinois. Habitats include wet prairies, prairie swales and sloughs, openings in floodplain and bottomland woodlands, soggy thickets, low areas along streams and ponds, fens, edges of marshes, and ditches along railroads and roadsides. American Bugleweed is found in degraded wetlands more often than other Lycopus spp.

Faunal Associations: A variety of insects visit the flowers, primarily for nectar, especially short-tongued bees, wasps, and flies. Other floral visitors include long-tongued bees, butterflies, skippers, and beetles. The caterpillars of Sphinx eremitus (Hermit Sphinx) feed on the foliage of this and other bugleweeds (as well as other members of the Mint family). Other insect feeders include such aphids as Kaltenbachia ulmifusa (Slippery Elm Gall Aphid), which feeds on the roots of Lycopus spp. during the summer, Hyalomyzus sensoriatus and Hyalomyzus eriobotryae, and Tiliphagus lycoposugus. Larvae of the gall flies Neolasioptera lycopi and Neolasioptera mitchellae also feed on these plants. Because the leaves of American Bugleweed are bitter-tasting, they are not often eaten by mammalian herbivores.

Photographic Location: A prairie swale along an abandoned railroad in Champaign County, Illinois.

Comments: American Bugleweed is a fairly typical member of the Mint family; it isn't particularly showy. There are several Lycopus spp. in Illinois, and they can be difficult to distinguish. However, American Bugleweed is easy to identify because its lower leaves have basal lobes that are narrow and deep. Other Lycopus spp. usually have leaves with wedge-shaped or rounded bottoms that are coarsely dentate along the entire length of their margins. If any lobes are present on the leaves of these latter species, they are more shallow and wide. Another common name of Lycopus americanus is Common Water Horehound.