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loosestrifes

Purple Loosestrife

Purple loosestrife (Lythrum salicaria) can be found growing in open riparian areas and wetlands in the Sea to Sky corridor. Introduced as a garden ornamental, due to its vibrant purple flowers perched on top of a tall stem, this beautiful plant aggressively crowds out native vegetation, impacting native plants, amphibians, birds and other wetland species. Purple loosestrife is estimated to be spreading at a rate of 115,000 hectares per year in the United States, destroying valuable wetlands.

Each plant is capable of producing up to 2.5 million seeds that can be dispersed by wind, water, wildlife, and humans. Plants can also reproduce from root fragments.

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The best way to identify purple loosestrife is by its square stems (roll it in your fingers) and opposite leaves. If you have purple loosestrife in your garden, remove it immediately. Pull or dig the plants out and ensure that all root fragments are removed to prevent re-growth. For large patches, there are relatively effective biocontrol agents, Galerucella calmariensis and pusilla. These beetles feed on the plant stems in their larval stage. For more information on biocontrol, see http://www.entomology.wisc.edu/mbcn/kyf501.html.

Yellow Loosestrife

General Information

Yellow (or garden) loosestrife (Lysimachia vulgaris) is an attractive wetland perennial that was apparently introduced to BC as an ornamental landscaping plant. Like purple loosestrife, it has the ability to invade and establish itself in wetlands and along lake and river shorelines.


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Yellow loosestrifeYellow loosestrife

Distribution

Yellow loosestrife is a native of Eurasia, where it occurs in fens, wet woods, lakeshores and riverbanks almost throughout Europe. In the Sea to Sky it has been found to date only in gardens, but because of the potential threat we hope that land owners/occupiers will remove the plant willingly.

Growth Habit

Garden loosestrife grows in moist habitats, such as fens, wet woods, wetlands, riparian areas, and lakeshores, but it may also be found in upland sites. It is a perennial plant 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. King County reports that the rhizomes from a single plant can be up to 15 feet long. Garden loosestrife produces bright yellow clusters of flowers from July to September. Its dense growth habit displaces native wetland vegetation and reduces habitat for fish and wildlife.

Management

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. It is not recommended to only pull this plant because it breaks off easily leaving rhizomes behind to regrow. No biological control agents are presently known and no research to discover biological control agents is currently being conducted.

Identification

  • Bright yellow flowers with five petals occur in a cluster at the top of the plant
  • Softly hairy stems and leaves on plants from three to six feet tall
  • Lance-shaped leaves arranged oppositely or in whorls around the stem
  • 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. Another loosestrife, Lysimachia punctata may be confused with garden loosestrife. Yellow loosestrife also has yellow flowers but these flowers occur all along the plant stem and not just at the top of the plant.  

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