Purple Loosestrife

North Pond Loosestrife

Loosestrife Invasion
An infestation of Loosestrife has been identified on the west shore of North Pond. This is not a new discovery, and it has been attended by the local landowner with mediocre results. We are planning to expand the resources and the method of removing this invasive plant with the goal of total eradication within the next several years. 

Landowners on North Pond should be extremely aware of this threat, and be hyper vigilant about identifying any additional locations of infestation as soon as just one plant is observed. The future of the pond could be at stake.

The Source

Loosestrife Plant Blossoms
Purple loosestrife (Lythrum salicaria), a beautiful but aggressive invader, arrived in eastern North America in the early 1800’s. Plants were brought to North America by settlers for their flower gardens, and seeds were present in the ballast holds of European ships that used soil to weigh down the vessels for stability on the ocean. Since it was introduced, purple loosestrife has spread westward and can be found across much of Canada and the United States.

The Problem

Purple loosestrife is a very hardy perennial which can rapidly degrade wetlands, diminishing their value for wildlife habitat. Wetlands are the most biologically diverse, productive component of our ecosystem. Hundreds of species of plants, birds, mammals, reptiles, insects, fish and amphibians rely on healthy wetland habitat for their survival.
However, when purple loosestrife gets a foothold, the habitat where fish and wildlife feed, seek shelter, reproduce and rear young, quickly becomes choked under a sea of purple flowers. Areas where wild rice grows and is harvested, and where fish spawn, are degraded. An estimated 190,000 hectares of wetlands, marshes, pastures and riparian meadows are affected in North America each year, with an economic impact of millions of dollars.
Purple loosestrife also invades drier sites. Concern is increasing as the plant becomes more common on agricultural land, encroaching on farmers’ crops and pasture land.

The Challenge

Many organizations throughout North America have taken action to control the spread of purple loosestrife. Their response has been characterized by unparalleled cooperation. National wildlife services, state natural resource and environment agencies, universities, nursery trades associations, and conservation and community organizations have responded to the purple loosestrife invasion by raising awareness of the threat posed by this invasive plant, and how to prevent its spread.

Individuals, resource managers and community groups can make a valuable contribution to conserving our wetlands for future generations by containing Loosestrife as soon as it is identified in a new location, preventing further spread into additional areas.

How to identify Purple Loosestrife

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.

Perennial Rootstock: On mature plants, rootstocks are extensive and can send out up to 30 to 50 shoots, creating a dense web which chokes out other plant life.

How to control Purple Loosestrife:

Controlling the spread of purple loosestrife is crucial to protecting vital fish, wildlife and native plant habitat. Purple loosestrife can easily spread if improper control methods are used. The following simple guidelines will ensure that your efforts to control the spread of purple loosestrife are effective.
Estimate the size and density of the infestation, and choose one or more appropriate loosestrife control options.

  • Digging & Hand Pulling: Pulling purple loosestrife by hand is easiest when plants are young (up to two years) or when in sand. Older plants have larger roots that can be eased out with a garden fork. Remove as much of the root system as possible, because broken roots may sprout new plants.
  • Cutting: Removing flowering spikes will prevent this year’s seeds from producing more plants in future years-- remember each mature plant can produce over 2 million seeds per year. Also, remove last year’s dry seed heads, as they may still contain seeds. Finally, cut the stems at the ground to inhibit growth.
  • Biological Control: In areas of severe purple loosestrife infestation, manual and chemical control efforts are ineffective and may in fact contribute to the problem. However, the use of specially selected insects that feed on purple loosestrife is being studied to determine the effectiveness of this method for long-term control in these higher density areas. 
  • Chemical Control: If an infestation is in a dry, upland area, and on your own property, an approved herbicide can be applied to individual plants by selective hand spraying. Broadcast spraying is not recommended as it kills all broad-leaved plants, leaving the area open to further invasion from nearby sources of purple loosestrife. This also provides an opportunity for seeds present in the soil to sprout.
  • Chemical control is used in the United States to control purple loosestrife near or in water. NOTE: In the U.S. a permit is required; call the Maine natural resource agency for more information.
Information on Purple Loosestrife courtesy of  Minnesota Sea Grant Program
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