The most identifiable characteristic of purple loosestrife is the striking rose to purple colored flowers. The flowers are arranged on a spike, which can be a few inches to 2 feet long. Each flower has 5 to 7 petals arising from a cylindrical green tube. The plant usually flowers from late June to Mid-August. The seed capsule is two celled and contains many very small seeds with over one half million seeds per plant possible. Roots become thick and woody in mature plants. The aerial shoots die in the fall and new shoots arise the following spring from buds at the top of the root crown. Stems are typically square or ridged to feel square and covered in fine hairs. Leaves are also finely pubescent mainly under, they are opposite or whorled, tapered to a point about 3 to 4 inches long.

This plant is difficult and tiresome to remove by hand, made harder with the heavy wet soil. In small new infestations some have had success using hand removal, but diligence is required. Several herbicides labeled for aquatic use work well, such as: Habitat, Garlon 3A, Accord and others. If you choose to use herbicide it is advisable to determine where the water will end up to avoid crop damage. Biocontrol insects are available and have been very effective over the long term.
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Modified from Selected Noxious Weeds of Eastern Oregon, Gary Page, Malheur County Weed Inspector.