Tuesday, July 29, 2008


Purple Loosestrife -- The Beautiful Invader
© 2008 Dave Spier
Purple Loosestrife is a tall, wetland plant sporting beautiful magenta flowers with six (sometimes four or five) petals surrounding a small yellow center. Clusters of these blossoms grow in dense whorls around a fuzzy, square stem. Pointed leaves grow in opposite pairs (sometimes whorls of three) below these flower spikes. The species is native to Europe. As early as Roman times, it was tied to the yokes of oxen in the belief that it appeased or ended strife and unruliness between the animals as they plowed. It was said to "loosen strife," hence the name loosestrife.
How could such a beautiful plant be a problem? We'll get to that in a moment.
Purple Loosestrife (Lythrum salicaria) was brought to eastern North America in the early 1800's to be used in flower gardens. If it had stayed where it was planted, we'd have little trouble. Since then it has spread westward across much of Canada and the United States. Loosestrife is a hardy perennial that takes over wetlands, crowding out the native cattails that our wildlife depends on. To give you an example, Black Terns (a declining species) depends on old, broken cattails for nesting material. The stiff, almost woody stems of loosestrife are not readily broken. Loosestrife is almost worthless from wildlife's point of view. For the most part, nothing eats it, although I once saw sparrows feeding on the seeds in late summer.
Loosestrife can also encroach on drier crop fields and pastures where it becomes a more direct economic issue. Each mature plant can produce up to 2.7 million seeds in one growing season. The rootstock also sends out 30 to 50 shoots that create a dense, monocultural web underground. This effectively chokes out "competing" vegetation.
On this side of the Atlantic, there are no natural controls for Purple Loosestrife. Our wildlife does not eat it or use it for breeding habitat. In Europe, over 100 insects feed on various parts of the plant. From these, five beetle species were selected and introduced into this country under controlled (caged) conditions. Some of the testing was done at Montezuma National Wildlife Refuge near the visitor's center east of Seneca Falls, NY. After determining that these beetles posed no threat to our desirable vegetation, they were released into the wild. Two of the insects feed on the leaves and new shoots; these are the kind released at Montezuma. A third beetle, a type of weevil, bores through the roots. The last two species eat the flowers. Some of the beetles were also released at Blue Cut Nature Center between Newark and Lyons in Wayne County, NY.
While these natural insect controls spread and multiply, a number of other steps need to be taken. So-called "sterile" varieties of garden loosestrife have been shown to cross-pollinate with wild Purple Loosestrife and produce viable seeds. Gardeners are asked to avoid planting loosestrife or any of its 26 cultivars. If it already grows in your garden, cut off the flower spikes as soon as the petals begin to drop and dispose of them in a plastic bag. Incineration is effective, but generally prohibited. If you are planting wildflowers, check the seed mix packets and make sure there is no loosestrife. Small infestations of loosestrife can be controlled by digging and hand pulling. Larger patches can be controlled by constant cutting. Chemical control usually requires a permit because of the danger to wetlands. Check with the Department of Environmental Conservation if you live in New York State or the state agency where you live.
In areas where loosestrife has already taken over a marsh, the best we can probably do for now is admire the beautiful color and wait for the beetles to arrive.
Contact Dave at northeastnaturalist@yahoo.com
(This copyrighted article and photo first appeared in The Times of Wayne County, July 28, 2008. All rights reserved.)

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