Purple Loosestrife

This is a non-native species with attractive blooms that has become a serious nuisance that outweighs its worth as an ornamental. Infestations result in dramatic disruption in water flow in rivers and canals, and a sharp decline in biological diversity as native food and cover plant species, notably cattails, are completely crowded out, and the life cycles of organisms from waterfowl to amphibians to algae are affected. A single plant may produce up to three million tiny seeds annually.