What is it?
Purple loosestrife is a tall, perennial wetland plant with reddish-purple flowers, which may be found in sunny wetlands, wet meadows, river and stream banks, pond edges, reservoirs, and ditches. It is native to Europe and Asia, and is now responsible for a considerable amount of the degradation to wetland habitats throughout the United States.
Is it here yet?
Yes, purple loosestrife has been documented throughout Washington.
Why should I care?
Purple loosestrife forms dense stands which outcompete native plants for space, light, and pollinators and provide poor habitat for waterfowl. It alters the structure and function of wetlands, clogs waterways and irrigation systems, affects rice and other agricultural production and reduces livestock forage quality.
What should I do if I find one?
How can we stop it?
Remove any plants from gardens to reduce seed sources and do not plant purple loosestrife. The Washington State Department of Agriculture devotes significant resources to managing this species under the Control of Spartina and Purple Loosestrife regulation (Chapter 17.26 RCW, Chapter 16.752 WAC). Purple loosestrife is listed as a Class B Noxious Weed in Washington, meaning it is designated for control in certain state regions.
What are its characteristics?
- Purple loosestrife can grow up to 6 feet tall and 4-5 feet wide.
- Its stems are square and a plant may have more than 30 stems.
- Small reddish-purple flowers grow in dense, showy spikes at the top of each stem.
- Leaves are opposite, hairy, and lance-shaped.
How do I distinguish it from native species?
Similar-looking native plants include:
- Fireweed, which has much larger flowers, alternate leaves, and does not grow in wetlands.
- Spirea, which has flowers arranged in clusters and oblong, alternate leaves.
- Native primrose loosestrifes, which are yellow-flowered.
- Native hyssop loosestrifes, which are shorter with white to rose petals.