Purple Loosestrife

Habitat: Purple loosestrife can be found in either the floodplain or emergent plant community. It commonly occurs in freshwater and brackish marshes, along the shores of lakes, ponds and rivers, ditches, and other moist areas. It is a successful colonizer and potential invader of any wet, disturbed site in North America.

 The magenta flower spikes of the Purple Loosestrife.

The magenta flower spikes of the Purple Loosestrife.

Description: When mature (after 3-5 years), purple loosestrife may be over 2 m tall. One plant may have over 30 flowering stems. Leaves are lance-shaped, entire, are usually opposite and arranged in pairs. However, they can be alternate or found in whorls of three. Stems are square in cross-section (sometimes 5 or 6 sided) and are sturdy and may be somewhat woody at the base. The plant bears magenta flower spikes that consist of many individual small flowers, each with 5-6 petals and small yellow centre. Seed capsules form in mid to late summer, and each capsule contains many small seeds.

Origin and Range: This infamous wetland invader is from Europe, northern Africa, and Asia. It was introduced to North America on several occasions: intentionally as a garden herb and accidentally in ship ballast. Purple loosestrife is now widespread in New Brunswick, being found in disturbed areas and in natural areas along river shores and in shoreline wetlands. It is very common along the lower Saint John River and is still spreading.

Annual Cycle: Purple loosestrife is a perennial that reproduces by seeds and rhizomes (root- like underground stems). Purple loosestrife blooms from June until September. A mature plant may produce up to 2.5 million seeds per year. Seeds can remain dormant in the ground for several years before germinating in late spring or early summer.

Look Alikes: It is often confused with fireweed (Chamerion angustifolium),which has a rounded stem and leaves arranged alternately;
blue vervain (Verbena hastata), which has toothed leaves; blazing stars (Liatris spp.), which only have one flowering stalk.

Impacts: Purple loosestrife quickly establishes and spreads, outcompeting and replacing native grasses and other flowering plants that provide high quality food and habitat for wildlife. It forms dense stands that restrict native wetland plants and alter the structural and ecological values of wetlands.

 Purple Loosestrife.

Purple Loosestrife.

 The stems of Purple Loosestrife are square in cross-section. 

The stems of Purple Loosestrife are square in cross-section.