Purple Loosestrife (Lythrum salicaria) is a perennial that originated in Europe and spread to North America in the early 19th century. The weed was originally introduced as an ornamental plant and for medicinal use. It was also introduced as a contaminant in ship ballast.
Purple Loosestrife grows 4 to 10 feet tall. The square rigid four-sided stems have fine hairs and are reddish purple. Leaves are oppositely attached and slightly heart-shaped at the base coming to a point at the tip. Each weed produces a showy spike of bright purplish flowers on a tall stem, visible from June until September. Each weed produces up to 3 million seeds and 1 foot of root expansion annually. Seeds are easily spread by water movement, caused by aquatic wildlife, livestock and humans.
This rapid, aggressive weed expansion crowds out native grasses, in particular common cattails. This expansion will reduce good ground cover, food and nesting sites for many wetland animals including ducks, geese, frogs and toads.
1) Physical removal is an option for seed and root reduction. Weed raking (Water Weed Rake) or weed cutting (Weed Razer Pro) can be difficult because new growth can sprout from seeds and root fragments left behind.
2) Loosestrife weevils and beetles feed on weed leaves. The larvae also emerge from their eggs and destroy tender leaf buds, burrow into the root or consume flowers.
3) Aquacide Pellets are a 2,4-D based, aquatic herbicide that is best applied early spring as new submersed weeds begin to appear. Repeat treatment 3-5 weeks after the first application may be needed to kill the entire root system.
4) Aqua Neat Liquid and Shore-Klear Liquid are both glyphosate based and best used for emersed aquatic weed control. Apply mid-season when all the weeds are above the water surface and in full bloom. Again, repeat treatment 3-5 weeks after the first application may be needed to kill the entire root system.
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