General Information About Water Primrose (Ludwigia hexapetala)
Water Primrose is a perennial herb that can be found creeping along the shoreline, floating on the water surface, or growing upright. It is a robust plant with bright yellow, showy flowers and willow-like leaves. It is a non-native species originally from South America and the southern United States and has been introduced into Europe and northern North America. In Washington water primrose has established in the drainage canals in the Longview/Kelso area. A new site was also recently discovered in King County.
Because of its showy yellow flowers, this plant is being sold as an ornamental species. Lake residents are strongly discouraged from planting water primrose in lakes, private ponds, in a flood zone, or in natural waterbodies. These plants are very invasive and aggressive and will form very dense mats of vegetation. As of January 2001, these plants will no longer be offered for sale in Washington.
Growth Habit
Water primrose grows in dense mats along shorelines and
out into the water. It
favors the margins of lakes, ponds, ditches, and streams. It blooms
throughout the summer. This photograph shows water primrose growing along
a ditch bank in Longview. It reproduces by seeds and by plant fragments.
Management
The Longview Diking District uses mechanical methods to remove water primrose and other noxious plants from the canals and ditches in Longview/Kelso. Other methods such as cutting, covering with opaque materials, and using the aquatic herbicide (Rodeo®) may be effective. It is not likely that grass carp would find water primrose to be palatable.
Identification
Water primrose can be identified by its sprawling growth habit and showy yellow flowers. Look for the following characteristics:
- Bright, yellow flowers; normally with 5 petals.
- Alternately-arranged, slightly hairy, willow-like leaves.
- Dense sprawling, tangled mat of vegetation.
Water primrose can be confused with other introduced water primrose species. If you think you have this plant growing around your pond or lake contact your county or local noxious weed control board for positive identification.
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