Purple loosestrife

Native to Eurasia, purple loosestrife prefers moist soils which can be found near wetlands, lake and river shores, ditchbanks, marshlands, freshwater tidal flats, and riparian meadows. However, purple loosestrife can tolerate a wide range of growing conditions including partially shaded areas, calcareous and acidic soils, and standing water. Sometimes if the plant is already well established it can survive on drier soil types such as pastures or croplands. In British Columbia, purple loosestrife is primarily in the south, particularly on Vancouver Island, the Lower Mainland, Fraser Valley, and the Okanagan.

• Invades wetlands, stream and river banks, and shallow ponds where it displaces valuable habitat.
• Can form monospecific stands, dominate aquatic plant communities, and reduce biodiversity.
• Dense infestations can clog canals and ditches, impeding water flow.
• Reduces the forage value of land for livestock, and decreases the palatability of hay.

The most effective way to ensure that your lands do not become infested with purple loosestrife is by prevention. Here are some recommendations to prevent invasion:

• Regularly patrol your property for purple loosestrife plants and immediately control or remove infestations before seed set.
• Cooperate with adjacent landowners and encourage them to take action to reduce purple loosestrife spread.
• Immediately re-vegetate disturbed, bare soils with a suitable seed mixture that provides dense, early colonization to prevent weed invasion.
• Do not move contaminated soils to a new area.
• Take special care when controlling purple loosestrife near streams, or ditch lines, to prevent the movement of seeds and plant parts downstream.
• ‘Clean, drain, dry’ boats and remove plant material and soil prior to leaving a loosestrife infested area.
• A few native and ornamental alternatives to plant instead of purple loosestrife include: Blazing Star, Tall Delphinium, Bloody Iris, Hardhack, and Spike Speedwell.

• Small infestations can be removed by hand pulling or digging before seed production and when plants are young. Since purple loosestrife reproduces through fragmentation, special care must be taken to ensure all plant parts are removed and don’t move downstream.
• Tarp or bag all removed plants, plant parts, and seeds and dispose of at a landfill.
• Mechanical control for large infestations has so far been unsuccessful.
• There are currently no chemical control options for purple loosestrife in BC due to its proximity to water.
• As a biocontrol option, the root boring beetle (Hylobius transversovittatus) and two species of leaf eating beetles (Galerucella calmariensis and Galerucaella pusilla) have proven effective against purple loosestrife in B.C.