Water hyacinth (Eichornia crassipes) is a floating water plant that blooms randomly on a single day, at any point in the growing season. The flowers are purple with a yellow spot on one petal and grow on 6-inch stems. The 6- to 12-inch leathery leaves keep the water hyacinth floating on the water surface, with its roots dangling below the water. The water hyacinth grows best in USDA Zones 9 through 11, where minimum annual temperatures don't drop below 20 to 25 degrees Fahrenheit, but can be grown as an annual pond plant in cooler regions during the summer.
Position your water hyacinth in full sunlight. Ensure that the water hyacinth's leaves are floating above the water surface.
Maintain water temperatures of 70 to 80 degrees Fahrenheit. Colder water can shock the plant or induce dormancy.
Keep the water pH levels around 6.5 to 7.5. Test your pond water's pH levels at least once each month and add pH balancing chemicals to the pond water when needed.
Feed your water hyacinth once each week during the growing season with an aquatic plant fertilizer. Follow the dosage recommendations on the label.
Keep your water hyacinth plants away from any fish that might feed on and damage them, such as koi. Most types of pond fish will simply use the water hyacinth's roots for spawning areas, however.