Garden loosestrife is an erect rhizomatous perennial that may attain a height of three feet or more. Both stems and leaves are soft and hairy to the touch. Lance-shaped leaves, 3 to 5 inches long, emerge from the stem in an opposite or whorled arrangement. The leaves are dotted with orange or black glands. The yellow, primrose-like flowers occur in a cluster at the top of the plant. Each flower has five petals and a calyx with reddish-brown margins. The fruit is a dry capsule-like body. Garden loosestrife spreads by both seeds and rhizomes. SPECIAL INFORMATION: The ability of garden loosestrife to invade and establish itself in wetlands threatens native plant communities. In spite of its more recent introduction, observations indicate garden loosestrife is far more abundant and appears to be outcompeting purple loosestrife. Therefore, in WASHINGTON, garden loosestrife is designated as a Class 'B' noxious weed and is also on the wetland and aquatic weed quarantine list. Sale, purchase, and transport of plants, plant parts, and seeds is prohibited. Management may be required by law in your county. Consult your local Noxious Weed Control Board for more information.

Habitat

Garden loosestrife occurs in moist habitats, such as fens, wet woods, lake shores, and river banks. It has also been planted as an ornamental and used for landscaping purposes, while admirers remain unaware of its invasive capability.

Management Options

Non-Chemical Management

Hand-pull to eliminate weeds.
Inorganic mulches, such as plastic, commercial "weed barrier" fabrics and other materials such as roofing paper, is an effective weed management option. Cover inorganic mulches with a thin layer of soil or organic mulch.
Digging and carefully removing all rhizomes will effectively eliminate single plants and small infestations.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Digging and handpulling is effective on very small populations only. Applications should be made by those holding a current aquatic pest control license. In Washington, a special permit is required for use of herbicides in aquatic sites. Contact the Washington Department of Ecology or the Washington State Noxious Weed Control Board for more information.

Images

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Caption: Garden loosestrife, flowering Photo by: King County Noxious Weed Control Program

WSU Extension

Hortsense