Perennial; blooms midsummer. Grows up to 7 ft tall. Upright bushy plant. Flowers pink to purple, possessing 5-6 petals and numerous on a long spike. Spreads by seed and spreading rhizomes that form dense, woody mats. Its showy purple flowers crown a vigorous plant that crowds out marsh vegetation required by wildlife for food and shelter. Decreased waterfowl and songbird production has been well documented in heavily infested marshes. This former ornamental species can be found along wetlands, stream banks, and shorelines of shallow ponds. Two defoliating beetles and a root weevil are currently used as bio controls.