General Information about Garden Loosestrife (Lysimachia vulgaris)

Garden loosestrife (Lysimachia vulgaris) is an attractive wetland perennial that was apparently introduced to Washington as an ornamental landscaping plant. However, garden loosestrife has the ability to invade and establish itself in wetlands and along lake shorelines. Where purple loosestrife and garden loosestrife grow together along Lake Sammamish shorelines, garden loosestrife is far more abundant and appears to be outcompeting purple loosestrife.

Garden loosestrife is a native of Eurasia, where it occurs in fens, wet woods, lake shores and river banks almost throughout Europe. In North America, it is naturalized in parts of Quebec, Illinois, Ohio, Kentucky, West Virginia, and Pennsylvania. In Washington, garden loosestrife is found along the shorelines of Lake Sammamish and Lake Washington in King County.  It was reported from Chambers Lake in Thurston County and also in Skagit County in 1996. It is also been reported from Stevens County (Loon Lake, 1998). The earliest herbarium collection of garden loosestrife from Washington was made in 1978 from the east-northeast corner of Lake Washington. Extensive  established populations along the shores of Lake Sammamish were observed in 1991.

Growth Habit

Garden loosestrife grows in moist habitats, such as fens, wet woods, lake shores, and river banks, but it may also be found in upland sites. It is a perennial that appears to remain in the vegetative stage for some time prior to blooming. The presence of a flowering specimen indicates it has been in an area for some years. Garden loosestrife spreads by seed and vegetatively (stolons). It produces bright yellow clusters of flowers from July to September.

Management

Response to herbicides is not currently known, however the aquatic herbicide Rodeo® (glyphosate) would likely provide the same control for garden loosestrife as it does for purple loosestrife. Garden loosestrife has been covered with black plastic at least one site on Lake Sammamish. This may be effective on very small populations or serve as a suppression tool where herbicides are not desired. Other alternatives have not been studied. Since the species has extensive rhizomes, hand pulling or digging would be limited to very small infestations. No biological control agents are presently known and no research to discover biological control agents is currently being conducted.

Identificationgarden loosestrife

Garden loosestrife has:

  • Bright yellow flowers with five petals occurring in a cluster at the top of the plant;
  • Softly hairy stems and leaves;
  • Lance-shaped leaves arranged oppositely or in whorls around the stem; and
  • Leaves dotted with black or orange glands.

Although when not flowering garden loosestrife may be confused with purple loosestrife, it does not have square stems like purple loosestrife.

Follow This Link for Technical Information About Garden Loosestrife

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