Circaea lutetiana is a perennial herb, to 70 cm tall, extensively colonial from rhizomes, roots associated with VA mycorrhizas, roots produced from rhizomes as new aerial shoots emerge in late spring (Brundrett and Kendrick 1988).
Leaves opposite, each pair at right angles to next, blade egg-shaped, 6-12 cm long, tip long-pointed, base rounded or slightly lobed, margin shallowly toothed.
Flowers white, tiny, petals 2, to 0.4 cm long, heart-shaped, deeply notched at tip, stamens 2, ovary inferior; inflorescence of spike-like clusters in upper axils, inflorescence to 20 cm, June-July.
Fruit dry to 0.5 cm long, covered with hooked bristles, 2-seeded, dispersed by adhesion to fur or clothing; fruits July-Aug. Dispersal to and establishment in new sites in successional forest, contiguous to old regrowth stands has been calculated at a rate of 1.64 m/yr. (Matlack 1994).
Wetland status: FACU.
Frequency in NYC: Occasional.
Habitat: Understories of moist to wet woodlands, floodplain forests, shade tolerant. Tolerates soil acidity down to pH 4.1 (Greller et al. 1990). Found in forest soil pH 5.6 (Gargiullo unpublished data). Often in disturbed habitats. Increases in forest gaps where light and moisture are more available (Moore and Vankat 1986).
Notes: Secondary chemicals include the flavonoids Astragalin, Icariside, Isovitexin as well as the phenolic Methyl Gallate (Kim, Y.C. & Kingston, D.G. (1996) “A new caprylic alcohol glycoside from Circaea lutetiana ssp. canadensis.” “Journal of Natural Products 59: 1096-1098. From: The Ecology of Commanster. commaster.eu).