Water hyacinth, or Eichhornia crassipes, is hardy in USDA Planting Zones 9 through 11. Fast-growing and rapid to spread, this plant loves still water in full sun. It blooms June through September, and nearly year-round under the best of conditions. Water hyacinth will live quite nicely in a shaded pond, but requires a hot summer and lots of full sun to produce the attractive lavender-blue flowers. Aquarium supply stores commonly retail the plant, and it grows wild in subtropical North America. While Eichhornia makes an attractive addition to the water garden, your state may regulate its possession.
Harvest wild water hyacinth by gently grasping a succulent upright bloom spike. Lift it slowly upward and out of the water. Its submerged roots may or may not resist slightly, as they are interconnected from one plant to the next. Just keep pulling, and one or more plants will release the root system.
Add a little of the pond water to a 5-gallon bucket and drop the hyacinth into it to transport.
Use sharp scissors to trim off any dead, yellow or damaged leaves or stems. These won't repair themselves. Trim the roots back to about 2 inches long. This will encourage the plant to reproduce.
Float a hula hoop in your pond. Drop the water hyacinth into the ring and set it afloat. Your plant will begin reproducing in about 2 weeks. Soon it will fill the floating ring with new plants, and quickly crowd it. Don't thin them, though. Not only do these plants crave crowded conditions, they won't bloom otherwise.
Trim the roots every 2 or 3 weeks if you want to accelerate plant growth and reproduction.
Toss another hula hoop ring into your water garden if you want to add more hyacinths. This is an easy way to confine these aggressive plants. Don't let them run wild and take over your water garden.
Lift a small piece of rooted water hyacinth for wintering over before the first predicted frost. Since the roots connect one plant to the next, just tear them apart with your fingers to separate the plants.
Fill a 5-gallon bucket about 3/4 full with some of the pond water. Set the bucket in the sunshine indoors and drop the water hyacinth into the water. The ideal temperature range is 60 to 70 degrees Fahrenheit, but as long as sustained temperatures don't drop below about 34 degrees Fahrenheit, the plant will survive the winter. Set it back out on your pond in the spring, after the last predicted frost for your area.