Lysimachia quadrifolia is a perennial herb, sparingly colonial from a 50 cm rhizome, roots associated with vesicular-arbuscular endomycorrhizal fungi (Berliner and Torrey 1989); stems erect, 0.3-1 m tall, finely hairy, usually simple, occasionally branched above.
Leaves usually in whorls of 3-6, usually 4, usually stalkless (sessile), blade 3-8 cm long, 0.2-0.7 cm wide, lance-shaped, tip pointed, base rounded to wedge-shaped (cuneate), hairy below, margin entire, winter rosette leaves maroon (Levine 1995).
Flowers yellow with red center, 1.3-1.6 cm wide, radially symmetrical, star-shaped, petal lobes 0.7-1.2 cm long, 0.5-0.9 cm wide, streaked with black, red at base; calyx lobes 0.4-0.6 cm long, black dotted or streaked (Radford et al. 1968); solitary in upper 2-6 whorls of leaf axils, each on a long slender stalks, topmost whorls sometimes flowerless (Radford et al. 1968); insect pollinated (Fern 2004); blooms July-August.
Fruit dry, a capsule 0.3 cm long, cupped by old calyx, splitting open at sutures; seeds 0.2 cm long, dark brown, number variable; fruits Aug.-Oct.
Wetland status: FACU-.
Frequency in NYC: Frequent.
Habitat: Open areas or bright understory of undisturbed open woods. Found in forest soil pH 4.8-5.0 (Gargiullo unpublished data).
Notes: Has been used as a medicinal (Fern 2004). Winter plant with slender, erect stalk, may retain old sessile leaves and calyx remnants (Levine 1995).