U.S.

Associated Press
In this April 26, 2012, photo, Japanese knotweed grows on a stream bank in Bethel, Vt. The flood waters of Tropical Storm Irene and work to remove silt and restore roads afterward had an unintended consequence: they spread Japanese knotweed, an invasive plant that has already clogged some river banks and roadsides in Vermont. (AP Photo/Toby Talbot)

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