Ecology and Management Potential for Purple Loosestrife (Lythrum salicaria)

Purple loosestrife (Lythrum salicaria), an exotic wetland plant from Eurasia, has become widespread in the northeast and northcentral regions of the U.S. and Canada. When it becomes established in a wetland, it crowds out most native plant species, and can form dense stands either in standing water or on moist soil. This results in decreased plant diversity and the loss of food and cover species valuable to wildlife. Some attempted control methods, such as controlled burning and water-level manipulation have proven to be unsuccessful. Other control measures, including mechanical cutting, replacement, and cattail competition, have shown encouraging, but inconclusive, results. This study was therefore initiated to further explore the possibility of controlling purple loosestrife through competition with cattails (Typha angustifolia) in mixed stands. A competitive edge was given to Typha by cutting Lythrum and selectively fertilizing Typha. First-year results of the study showed a significant decrease in Lythrum biomass as a result of cutting treatments. Cutting did not significantly reduce resprouting Lythrum stems, as Lythrum resprouted in greater numbers than Typha, but Typha sprouts grew faster and increased in biomass more quickly than Lythrum sprouts. With carbohydrate replenishment to the roots reduced, it is expected that Lythrum biomass will be reduced in subsequent years. The stress caused by cutting, and increased shade by the Typha canopy, may help to control purple loosestrife spread