It generally destroys the preferred nesting habitat of many waterfowl and other marsh-dwelling birds. Additionally, the closely spaced clumps do not provide brood cover. A few bird species, however, such as black-crowned night herons and piedbilled grebes, occasionally nest in purple loosestrife. The red-winged blackbird will probably benefit from an increase in purple loosestrife. These birds construct their nests in the dead stems of the previous season.
Purple loosestrife is a highly competitive weed that replaces native wetland communities.
It is classified as a noxious weed in many states. The continuity and configuration of wetlands strongly influence the expansion of local infestations because purple loosestrife is primarily spread by floating seeds or propagules. Isolated wetland basins are relatively safe from purple loosestrife spread, whereas wetland complexes connected by a common waterway are highly susceptible. Streams with steep gradients are less susceptible than streams with low gradients because they have few backwater areas for aquatic emergents to take hold. Until then, mechanical and chemical control measures should be used on a site specific basis.