Purple loosestrife: Looks can be deceiving

Purple loosestrife’s ability to spread contributes to its success as an invader. (Vermont Fish and Wildlife Department)

We were driving south on I-81, going to the New Jersey shore to visit some friends who live there. Passing some marshy areas, my wife made a comment about the beautiful purple flowers that seemed to grow everywhere the soil was wet enough. Field edges, swampy areas, roadside ditches, wet pastures, stream banks, they all seemed to have an abundance of these plants with the pretty purple blossoms.

“They’re pretty all right, but that plant is an invasive species and a threat to most wetlands,” I informed her.

“The plant is called purple loosestrife and it can take over any wet or moist area, driving out native plants, insects and amphibians,” I continued with smug erudition.

As we drove along, I continued my unsolicited lecture about the plant everyone seems to see but knows little about. I explained to my wife that the problem with purple loosestrife is that it forms dense stands in wetlands and eventually outcompetes the native vegetation. Because it does so, biodiversity is restricted, and it displaces plants with nutritive value for local wildlife while destroying waterfowl habitat. The plant has been around since the beginning of the 20th century, but may have gotten a good toehold when some government agencies used it to control erosion in roadside drainages. Furthering its spread, the plant was once offered for commercial sale and planted in home gardens.

Purple loosestrife is an erect, perennial herb standing three to 10 feet tall, but its average height is around five feet. This is the time when the plant is most noticeable to passing motorists because it blossoms from July through September with purple flowers that are located in long spikes at the tip of its branches. Purple loosestrife’s ability to spread contributes to its success as an invader. One adult purple loosestrife plant can produce several million seeds annually and the seeds remain viable for years until soil conditions become favorable for germination. If that’s not enough, the seeds can easily be dispersed and transported by wind, birds, small animals, boots, shoes, boats and even car tires. To make things even worse, purple loosestrife is also capable of resprouting from broken stems, underground roots and plant fragments. Possibly making it a good candidate as the plant from hell, if it’s mowed, the cut stem pieces will send out new roots and form new plants.

Purple loosestrife can be controlled by physical, biological or chemical means, but the best way seems to be biological. Five species of beetles have been approved for use by the USDA and they have been released in the United States as biocontrol agents. States like New Hampshire and Minnesota have reported some measure of success controlling plant populations after the beetles were introduced. Biologists hope the beetles will eradicate up to 80 percent of the plants, but that may take another 20 years. The sad truth is that the plant can’t be totally controlled, but its density in overrun areas can be managed.

Categories: New York – Mike Raykovicz

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