Garden Loosestrife

Lysimachia vulgaris

WA B desig. Primulaceae
Data Maturity Baseline

Washington State Classification

Class B — Control Required (Designated)

Garden loosestrife is invasive perennial that can form dense stands of growth in Washington's wetlands and shorelines.

Required control in Region 1 (all western Washington counties)

Quick Reference

Type
perennial herb
Origin
Europe, Asia and Northern Africa

Identification

Growth Habit

It is an upright, rhizomatous perennial that can grow to a height of 3 feet or more, forming dense stands. Stems and leaves are soft and hairy. Flower clusters bloom in the summer.

Leaves

Leaves are opposite or whorled, lance-shaped, 3.1 to 4.7 inches (8-12 cm) long, dotted with black or orange glands and softly hairy.

Flowers

Flowers are yellow, primrose-like and occur in a cluster at the top of the plant and in the upper leaf axils (the upper angle from where the leaves and stem connect). Each flower has 5 petals and sepals with reddish-brown margins.

Fruit & Seeds

Seeds in capsules that open by valves.

Impact

Garden loosestrife is invasive perennial that can form dense stands of growth in Washington's wetlands and shorelines. Its behavior is similar to another noxious weed, purple loosestrife (Lythrum salicaria), that it appears it can outcompete.

Ecology & Spread

Habitat

Garden loosestrife occurs in moist habitats such as fens, wet woods, lake shores, wetlands and streambanks. Please click here to see a county level distribution map of garden loosestrife in Washington.

Spread Mechanisms

seed vegetative fragments human activity

Reproduction

Garden loosestrife spreads by seeds and rhizomes.

Regional Notes — Puget Sound

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Control Methods

Mechanical

  • Small populations may be covered with black plastic or a heavy tarp, make sure to secure edges and watch for plants trying to grow through holes or gaps. Other alternatives have not been studied. Since the species has extensive rhizomes, hand pulling or digging would be limited to very small infestations or new infestations.

Cultural / Prevention

  • 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.