PURPLE LOOSESTRIFE

(Lythrum salicaria)

Purple loosestrife is an invasive perennial plant from Eurasia that is primarily found in wetland areas.

ORIGIN
It’s unclear exactly when purple loosestrife first appeared, but it was first introduced to the eastern North American garden trade in the early to mid-1800s. This plant may also have been purposely introduced from Europe for herbal uses or from seeds contained in livestock feed or bedding.

HABITAT
Purple loosestrife can now be found throughout the United States and southern Canada. Optimum habitats include freshwater marshes, open stream margins, and alluvial floodplains. The plant also occurs in wet meadows, river banks, and edges of ponds and reservoirs. It tolerates fluctuating water levels and excels in disturbed sites, such as construction sites for docks or marinas. Purple loosestrife is often associated with cattail, reed canary grass, and other moist soil plants.

IDENTIFICATION
Erect (1-2 m), perennial herb with a square, woody stem and opposite or whorled leaves. Purple loosestrife flowers from July through August, and is named for its bright purple flower spikes. One plant may grow as an individual stalk or as several stalks clumped together.

SPREAD
One loosestrife plant can produce three million seeds annually. The seeds are long-lived and easily dispersed. Once established each plant is capable of resprouting from broken stems or roots. Humans have also played their part in the spread of these invasive plants across North America. Since the purple loosestrife has such a lovely purple flower a number of folks have planted them in gardens, and some nursery businesses have even sold the plant or put its seeds in their wildflower mixes.

Distribution of Purple Loosestrife

IMPACTS

• Purple loosestrife negatively affects wildlife and agriculture by displacing and replacing native flora and fauna, and thus eliminating food and shelter for wildlife.
• By reducing habitat size, purple loosestrife may have a negative impact on fish spawning and waterfowl habitats.
• Affects agriculture by blocking flow in drainage and irrigation ditches and decreasing crop yield and quality.

PREVENTION AND CONTROL
Since 1997 purple loosestrife has been prohibited from sale, transport, and propagation in Pennsylvania.

Traditional control techniques include:

• Manual—pulling the plant out by the root or burning
• Biological—releasing of exotic beetles (European Galerucella) that specialize in eating purple loosestrife
• Chemical—spraying dense stands of purple loosestrife

FOR MORE INFORMATION ON PURPLE LOOSESTRIFE

• Michigan Sea Grant Purple Pages
• Purple Loosestrife in Michigan
• Purple Loosestrife: What You Should Know, What You Can Do
• Aquatic Plant Management: Purple Loosestrife
• Highly Disruptive Exotic Plants
• Purple loosestrife in Michigan: biology, ecology, and management.

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