Purple loosestrife (Lythrum salicaria)

Invader Type: 
  • Plant

SPECIES UPDATE

04/09/13
Cooperative Weed Management Association assist communities with the identification and control of non-native invasive plants in the Upper White River watershed

Control

Mechanical Control: 

For small infestations:

  • Hand pull individual plants by grasping each stem at its base and pulling slowly to remove all the root.
  • Break off flower heads before they go to seed.
  • Put the discarded vegetation into a plastic garbage bag to decompose.

For large infestations:

When funding allows, the Vermont Department of Environmental Conservation’s Water Quality Division releases beetles near large patches of loosestrife. Call 802-241-3777 to report locations of loosestrife or learn more on-line at www.vtwaterquality.org.

Photos

Photos: 

Description

Identification: 

Flower: Individual flowers have five or six pink-purple petals surrounding small, yellow centers. Each flower spike is made up of many individual flowers.

Leaves: Leaves are downy, with smooth edges. They are usually arranged opposite each other in pairs which alternate down the stalk at 90 degree angles, however, they may appear in groups of three.

Stalks: Stalks are square, five or six-sided, woody, as tall as 2 meters (over 6 feet) with several stalks on mature plants.

Source: Minnesota Department of Natural Resources.

http://www.dnr.state.mn.us/invasives/aquaticplants/purpleloosestrife/id.html

Reproductive Strategy / Lifecycle: 

Mature purple loosestrife plants can produce up to 1 million seeds, most of which are viable.

Habitat: 
Purple loosestrife invades Vermont’s fields, marshes and bogs.
History: 
Introduced as an ornamental.
Legal Status: 

Class B Noxious Weed

References: 

Photos: J.Randall, TNC; S. Kuebbing, TNC: (c) S. Dewey Utah State University; (c) T. Webster USDA Agricultural Research Service.

Threat

Ecological Threat: 
  • As the leaves of purple loosestrife (Lythrum salicaria) decompose in water, they secrete high levels of tannic acid. Research shows that American toad (Bufo americanus) tadpoles suffer higher mortality rates in this highly acidic environment.
  • Each purple loosestrife plant can produce 1,000,000 seeds, 97% of which are viable.
  • Wetlands filled with purple loosestrife stands do not contain the grasses, sedges, aquatic vegetation and native shrubs that were once there. Purple loosestrife does not support as many insect species as native plants. Native birds can no longer  find the food sources or quality nesting habitat that they could once find in the wetland.