Department Header For Noxious Weed Division
Yellowstone County, Montana
Noxious Weed
Weed Information Contact Department

Purple Loosestrife
(Lythrum salicaria L.)

Loosestrife family - Lythraceae


Purple Loosestrife

Photo from Weeds of the West

Purple Loosestrife Stalk 1

Purple Loosestrife Stalk 2

Purple Loosestrife Leaf

Purple Loosestrife Plant

Purple Loosestrife Bloom

Purple Loosestrife Mature

Photos from Montana Weed Control Association

Growth Habit: Perennial, erect to 8 feet tall, associated with moist or marshy areas.

Leaves: Simple, lance-shaped, smooth margins, opposite or whorled.

Stem: Branched, terminating in flowering stalks.

Flower: Rose-purple flowers having 5-7 petals and numerous stamen, in long, vertical recemes.

Roots: Large, fleshy, adapted to aquatic sites.

Seeds: Oval, 1mm long seeds develop in capsules that burst when mature. More than 2 million seeds can be produced by an average sized plant.

Reproduction: Primarily by seeds, but can spread through cut stems and fragmented roots

Habitat: Aquatic sites such as marshy areas, streams, and stream banks, ponds, irrigation canals and ditches support the worst infestations.

Biological Controls: Black-margined loosestrife beetle (Galerucella calmariensis), Golden loosestrife beetle (Galerucella pusilla), Loosestrife root weevil (Hylobius transversovittatus).

Herbicides: None used in Yellowstone County at this time.

Produced by Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp.


Video Supplied By Montana Weed Control Association