Water hyacinth is a South American native, but the plant has become naturalized in much of the Southern United States. This beautiful plant can grow up to 3-feet tall and is so invasive that some states prohibit its cultivation. Hyacinths left on their own to grow in a pond can spread to the point that they create a dense mat over the surface that can deplete oxygen and kill fish. Planting and growing water hyacinth is not a challenge; the challenge is to keep them from taking over your water garden.
Trim away all of the dead or broken leaves from your water hyacinth plant. Broken leaves will not repair themselves and can cause the plant to rot. Water hyacinths can thrive in most types of water without salt. They help prevent algae and their roots provide a spawning area for some fish as well as a home for insects that ultimately become fish food.
Toss your water hyacinth plant into the pond during the late spring and consider it planted. Water hyacinths have air filled leaves and heavy roots that keep them floating right-side up. Water hyacinths have long roots that are heavily branched and covered with black whiskers. The root systems helps remove fish waste from the water. Most water hyacinths grow 12- to 18-inches tall and can double every 12 days.
Fertilize your water hyacinth if their leaves turn yellow. Any type of fertilizer will work, just make sure that it's safe for the fish in your pond.
Remove water hyacinth from your pond or water garden at the end of the growing season in the fall. If you leave them in the pond, they will rot. Rake them out of the water, allow them to dry and then mulch them with your lawn mower.