Garden loosestrife, (Lysimachia vulgaris), also called yellow loosestrife, is a native of Eurasia that was introduced to North America as an ornamental. An invasive aquatic plant, it was recently discovered growing in Lake Whatcom near Bloedel Donovan Park.
Garden loosestrife invades wetlands, spreading by seeds and horizontal stems called rhizomes. Rhizomes can stretch across water for up to 15 feet, where watercraft can sever them, allowing pieces to float away and start new plants.
A perennial, garden loosestrife can grow to more than 3 feet long. It has soft, hairy stems and lance- to oval-shaped leaves that are several inches long and dotted with small black or red glands. The bright-yellow flowers cluster at the top of the stem.
Small patches can be stopped by hand-digging, if all of the roots are removed. More details: Whatcom County Noxious Weed Control Board.