Water Primrose
Ludwigia hexapetala
Washington State Classification
Class B — Control Required (Designated)
Water primrose is an invasive aquatic species that forms extensive mats, impairing water flow and shoreline activity.
Required control in Region 1 (all western Washington counties)
Quick Reference
Identification
Growth Habit
Water primrose is an aquatic perennial herb with robust, sprawling growth and showy, bright yellow flowers. Fibrous roots form from lower nodes on stems. It also produces white, hanging root-like structures.
Leaves
Leaves are alternately arranged along stems. Young leaves form rosette-like clusters. Mature leaves are willow-like in shape, up to about 4.75 inches long and are slightly hairy.
Flowers
Flowering stems are upright. Flowers are showy, yellow and have 5 bright petals, 0.6 to 1 inch (1.5 to 2.5 cm) long. Flowers are solitary on stalks that come from the leaf axils (upper angle of where leaf attaches to stem).
Fruit & Seeds
Capsules are formed that are up to 1.25 inches long and contain many small seeds.
Impact
Water primrose is an invasive aquatic species that forms extensive mats, impairing water flow and shoreline activity. It can dominate shoreline vegetation if introduced to lakes, rivers, ponds or streams. It is very difficult to control once established.
Ecology & Spread
Habitat
Water primrose is an aquatic herb which is found rooted and growing in shallow water to about 1 m deep; it is found in margins of lakes, ponds, ditches and streams. Please click here to see a county level distribution map of water primrose in Washington.
Spread Mechanisms
Reproduction
Water primrose spreads by seeds and by plant fragments.
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