Blue Mountains National Resources Institute

Wanted: DEAD!

Purple Loosestrife

Alias: Spiked willow-herb, long-purples, purple lythrum

• Stems: Up to 6 feet tall, 4 sided and branched.
• Leaves: Opposite, sessile, 1 to 4 inches long, whorled, lance-shaped, usually rough-hairy. In fall, they dry and turn bright orange.
• Flowers: 1 inch across with six crumpled purple petals on crowded, interrupted, elongated, terminal spikes. Long flowering season between June and September.
• Fruits: Two-celled, opening up to release seed.

Purple loosestrife is a perennial that is found in marshes, wet areas, stream courses, and ditch banks. It can spread by seed and by spreading densely matted, creeping, underground stems. It forms dense stands. It can produce 2.5 million seeds a year.

Control:

• Mechanical: First-year plants are easy to pull. Remove all plant material after pulling. It can be difficult to pull established plants, owing to the extensive root mat. Plant will resprout unless entire root is removed. Mowing might be effective if cuttings dry rapidly. Cutting off budding stalks during the flowering season works.
• Biological: Oregon Department of Agriculture has used a combination of four bioagents (two defoliators, a seed-boring weevil, and a root-boring weevil) to successfully control purple loosestrife on a site near Union, Oregon.
• Chemical: Spot application of herbicides approved for use in aquatic areas is effective. Consult your local weed control office for more information.

Report all sightings to your local Weed Board