Water Primrose can cause considerable problems as its dense floating mats diminish water quality and become a haven for breeding mosquitoes. Its creeping behavior can develop thick colonies interfering with recreational use of waterways and interrupt wildlife and fish habitats. The perennial begins along the shoreline standing erect but produces runners up to 16 feet long that can spread along the water surface. Roots develop at the runner nodes. It becomes very tangly and dense. Water Primrose has flashy bright yellow flowers with 5 petals. The flower is 1 to 2 inches in diameter. Lance-shaped leaves are green and sometimes red hued with an alternating position along the stem.
