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