Final Report (~8.3 mb pdf)
Species Specific Session Abstract
Purple Loosestrife
Steve Capel
Virginia Department of Game & Inland Fisheries
Purple Loosestrife, Lythrum salicaria, is an old world herbaceous perennial found in moist soil settings. It was introduced to North America in the early 1800s. It is fancied for its long spikes of showy purple flowers and as a nectar plant. It produces 300,000 to 500,000 seeds/plant, and the seeds retain viability for years. L. salicaria spreads by seed, fragments of root or stem, natural transport in flood waters and by wildlife and by gardeners.
L. salicaria is densely spread across New England, the Lake States and Pacific Northwest, and recedes in density to the south of these areas. As a consequence, in the Bay watershed it is most abundant in New York and Pennsylvania with lessening abundance in Maryland and Virginia. Loosestrife is a declared noxious weed in 27 states, including every state in the Chesapeake Bay watershed except Maryland.
Control of L. salicaria is most effective using 1% Triclopyr, though Rodeo also offers reasonable control. Two leaf-eating beetles (Galerucella spp.) and a root weevil (Hylobius sp.) have been released in Pennsylvania and Virginia as biological control agents. Mowing in late June or early July will keep the plant from going to seed, but does not reduce stand vigor.
Several hurdles must be overcome before an effective control program in the Chesapeake Bay drainage can become effective: (1) the impact of biological control agents on native loosestrife, (2) the opposition to control due to the beauty of the plant, (3) the extensive seed bank in many locations, (4) the myth of sterile hybrids, (5) the lack of a clear, effective chemical control, and (6) no clear agency in charge of control. There are several alternatives for horticultural use, including purple coneflower, joe-pye weed, dragonhead, turtlehead and butterfly bush.
![[Maryland Sea Grant]](http://www.mdsg.umd.edu/GIFs/h_footer_mdsg.gif)
![[Chesapeake Bay Program]](/issues/restoration/non-natives/workshop/cbplogo.gif)