Alternate name: Common Primrose-willow
Family: Onagraceae, Evening-primrose view all from this family
Description This coarse, shrubby weed with showy yellow flowers can grow in or near water, sometimes developing white spongy aerial roots resembling cypress knees.
Habit: introduced perennial shrub, subshrub, or herb; brownish-green stems, much-branched, hairy in youth; from woody taproot.
Leaf: usually alternate, lanceolate to broadly ovate, pointed, 2-6 in (5-15 cm) long, 0.5-1.25 in (1-3 cm) wide; fuzzy tan hairs above and below.
Flower: 4-lobed (rarely 5-lobed), bright yellow, 0.75-2 in (2-5 cm) wide; 4 wide, oval, veined petals, alternating with 4 narrow, pale green sepals, 8 stamens; petals dropping after one day.
Fruit: 4-angled capsule, held erect, 0.5-1 in (1-2.5 cm) long.
Flower Year-round, or April to November, depending on location.
Habitat Shorelines and shallow water: swamps, bogs, lakes, pond margins, ditches, canals, wet woodland openings.
Range Native to South America; introduced as an ornamental, and naturalized in the southeast U.S., from North Carolina to Florida to Texas, and in Puerto Rico.
Discussion Also called primrose willow, common primrose willow, Peruvian water primrose. An obligate wetland indicator. This plant forms dense colonies along shorelines, then grows out into the water, where it clogs waterways, damages structures, and out-competes native vegetation.