Garden loosestrife is an erect rhizomatous perennial that may attain a height of one meter or more. Both the stems and the leaves are softly hairy. Lance-shaped leaves, 8-12 cm long, occur on the stem in an opposite or whorled arrangement. The leaves are dotted with black or orange 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.
Beneficial: Flavanol glycosides extracted from Lysimachia vulgaris var. davurica are used in Chinese folk medicine for the treatment of high blood pressure.
Detrimental: The apparent ability of garden loosestrife to invade and establish itself in wetlands threatens the native character of this natural resource in Washington. The extent and impact of garden loosestrife on wetlands surrounding Lake Sammamish indicates it can be significantly aggressive and invasive. Purple loosestrife, a serious noxious weed in problem in many Washington wetlands, was first documented on Lake Sammamish in 1929. There is good reason to believe the garden loosestrife introduction to Lake Sammamish is considerably more recent. However, in spite of its more recent introduction, observations indicate garden loosestrife is far more abundant and appears to be outcompeting purple loosestrife.
Lysimachia vulgaris is an example of an exotic introduction to Washington that could have a serious negative impact on the native character of Washington's wetlands. Presently, this species has a limited distribution in Washington. The extent of garden loosestrife populations on Lake Sammamish illustrates that this species can be significantly aggressive and invasive. Control of this species will be complicated by two factors:
Lysimachia vulgaris 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 as illustrated by the photograph to the right.
Lysimachia vulgaris 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. The species appears to be increasing in the Ohio River Valley (Cusick 1986).
In Washington, wild populations of garden loosestrife are currently known from Lake Sammamish and Lake Washington and eastern Washington sites. Scattered clumps of Lysimachia vulgaris are known from the north and south end of Lake Washington. On Lake Sammamish, garden loosestrife is well established. Garden loosestrife has been seen along lake shores in Stevens County and also in Thurston County wetlands.
The only herbarium collection of Lysimachia vulgaris from Washington was made in 1978 by Dr. Bastiaan Meeuse. It is stored at the University of Washington herbarium. The collection comes from the east-northeast corner of Lake Washington near Juanita Junction. Extensive established populations along the shores of Lake Sammamish were observed in 1991.
Lysimachia vulgaris is a rhizomatous or stoloniferous perennial that appears to remain in the vegetative stage for some time prior to blooming. According to Cusick (1986), the presence of a flowering specimen indicates it has been in an area for some years.
Garden loosestrife spreads by seeds and rhizomes (stolons). The species flowers from July to September.
The King County Noxious Weed Control Board requires control of garden loosestrife (Class B noxious weed in Washington). They report that small areas of garden loosestrife seedlings can be dug up and larger isolated plants can be removed by hand if care is taken to remove all rhizomes. They do not recommend only pulling this plant because it breaks off easily leaving rhizomes behind to regrow. Garden loosestrife has been covered with black plastic at least one site on Lake Sammamish. This can be effective for controlling seedlings or on very small populations. It can also serve as a suppression tool where herbicides are not desired. King County reports that the aquatic formulations of glyphosate, triclopyr, and imazapyr are effective on garden loosestrife. No biological control agents are presently known and no research to discover biological control agents is currently being conducted.
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Yasukawa, K and M. Takido. 1988. Quercetin 3-Rhamnosyl (1--2) galactoside from Lysimachia vulgaris var. davurica. Phytochemistry. 27: 3017-3018.
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