Lysimachia terrestris is a perennial herb 40-80 cm tall, stem bluntly 4-sided, hairless, branched above, leaf scars leaving bamboo-like joints around stem; small, succulent bud-like bulblets form late in season in some leaf axes, often reddish, dropping to ground and forming new plants the following season.
Leaves opposite to subopposite, stalk short to none, blade 3-10 cm long, 0.7-2 cm wide (Radford et al. 1968), narrowly lanceolate, surface dull light green, soft, sprinkled with tiny dots (use lens), pointed at both ends, margins slightly rolled under (revolute).
Flowers yellow with dark lines, much like those of L. quadrifolia, petal lobes 0.5-0.7 cm long, narrow, elliptic; flowers stalks slender, ca 1 cm long; inflorescence a terminal raceme, flowers in whorls at each node; blooms June- July.
Fruit a dry capsule 0.3 cm long, cupped by persistent calyx lobes; fruits Aug.-Oct. (Hough 1983).
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Marshes, swamps.