Ludwigia sphaerocarpa is a perennial herb to 1 m tall, colonial from stolons, freely branched above, often red in full sun.
Leaves alternate, stalk 0-0.2 cm long, blade 5-10 cm long, to 1.5 cm wide, lance-shaped to linear, pointed at both ends, leaves of inflorescence much smaller.
Flowers green, no petals, sepals 4 from rim of flower base (hypanthium), stamens 4 yellow, ovary inferior, surrounded by hypanthium, stigma round, yellow; blooms and fruits July-Sept.
Fruit a rounded capsule to 0.4 cm, surrounded by old calyx lobes.
Wetland status: OBL.
Frequency in NYC: Rare (NYS S2 T; CT E).
Habitat: Wet soil, swamps.