Katherine Parys, USDA-ARS, Bugwood.org
Description: free-floating aquatic plant that has invaded aquatic areas throughout the eastern and southern portions of the United States. Plants can grow to 3 ft. (1 m) tall. The leaves are bright green, oval to elliptical, thick, up to 6 in. (15 cm) wide, and waxy with spongy petioles that often have a bulb-like base. Leaves are in a whorl arrangement and curve inward at the edges. Flowering occurs in late summer to early fall. The very showy blue-purple flowers are born on upright spikes with 8-15 flowers on the spike. Each flower has six petals with the uppermost having a yellow patch.
Ecological Threat: Invades lakes, ponds, rivers, marshes, and other types of wetland habitats. It can quickly form dense floating mats of vegetation (populations can double in size in two weeks!). These dense mats restrict light to the underwater environment, reduce the light availability for submerged plants and aquatic invertebrates, and deplete the oxygen levels.
Biology & Spread: The fruit is a capsule containing up to 450 seeds. The seeds are oval at the base with a tapering apex measuring 4 mm long and 1 mm wide and can remain viable for 30 years. However, this plant reproduces primarily vegetatively by stolons (runner stems).
In Oklahoma: Like Water Lettuce, Water Hyacinth is a significant problem in the states of the Gulf Coast. And also like Water Lettuce, Water Hyacinth is a popular plant for water gardens. Therefore, the degree of infestation along the Gulf Coast, its popularity in water gardens, and continued warming of the climate indicates that Water Hyacinth may become a problem in the future. We should continue to look for and eradicate any Water Hyacinth that appears to escape from garden habitats into natural areas.