Purple Loosestrife, invasive plant, aquatic

Purple Loosestrife (Lythrum salicaria L.)

A perennial plant that often grows near or in water. The purple flowers grow around the stem in a spike form. They have 5-7 petals. Leaves are lance-shapped and either opposite or whorled around the stem. It can grow up to 2 metres tall. It spreads by seed and by the roots. Stem fragments can also root. A single plant can produce up to 300,000 seeds.

LRISS Category: ERADICATE

Habitat & Ecology

It was introduced from Eurasia and first recorded in North American in the early 1800’s. It prefers wet areas in low elevations and grows in ditches irrigation canals, riparian areas and wetlands. It can tolerate up to 50% shade and acidic, calcareous soils. It needs moist conditions to reproduce but a mature plant can survive on dry soils for years.

Impacts

Purple loosestrife can form dense stands that impact plant and habitat diversity. These stands can also plug canals and irrigation ditches.

Management

New infestations can be minimized if removed when very small and before it sets seed. It is very important to reduce soil disturbance and promote native plant growth. The BC Government has released three bioagents that can damage the roots and leaves, stunt growth, and reduce seed production. There are 2 leaf-eating beetles and a root boring beetle. Please contact LRISS for biocontrol and all other treatment information.

References

Province of British Columbia. 2002. A Guide to Weeds in British Columbia.