A fast-growing tropical plant that floats on the surface of the water, water hyacinth (Eichhornia crassipes) produces lavender to pale blue-violet flowers in warm months. Native to tropical areas of South America and regarded as a noxious invasive weed across the southern United States, water hyacinth must be closely controlled by growing it only in ornamental water features. Refrain from growing it in natural waterways like streams, lakes or canals as well as any water feature that may flood and carry the plants into natural waterways. This plant survives outdoors year-round in U.S. Department of Agriculture hardiness zones 8b and warmer.
Fill an ornamental water feature or container like a pre-formed pond liner, whiskey barrel or in-ground garden pond with fresh water that is at least 6 inches deep. The water feature must receive at least eight hours of direct sunlight daily. There also must be no danger of frost.
Purchase water hyacinth plants from the plant nursery or pet supply store. Buy enough plants to cover no more than 1/4 of the surface area of your water feature.
Remove the water hyacinth plants from the bag or other container from the store and float them in the water in your water feature. Untangle any roots from the leaves and stems so that the roots dangle downward into the water.
Monitor the growth of the plants across the summer months. As the water and air temperatures increase, the faster the water hyacinth will grow and flower.
Remove excess plants when too much water surface is being covered according to your aesthetics. Destroy these plants by allowing them to fully dry out and die in the sun. Do not toss plants into other water bodies as the plants will proliferate without any management. Consider freezing plants in the kitchen freezer for a couple of days to ensure they are dead.
Allow the autumn frosts and freezes to fully kill the water hyacinth plants. Alternatively, bring one plant inside to overwinter and use again next summer. Place the plant in a bowl of water and place it in a warm, sunny window.