• Three species of water hyacinth, a flowering aquatic plant, thrive in ponds throughout North and South America. While native to South America, the hyacinth plant has spread to many countries in Europe and across the world. According to the U.S. Department of Agriculture, several types of hyacinth are considered dangerous and exotic species in North America. Despite their proclivity to overgrow and clutter waterways, hyacinths can make great additions to natural or decorative ponds. They suppress algae growth by consuming excess nutrients in the water and provide food or shelter for animal life.
  
  

Common Water Hyacinth

• The common water hyacinth (Eichhornia crassipes) is the hardiest, and possibly most prevalent, of the four species. With ovate leaves that measure several inches across, the common hyacinth produces a single spear of purple flowers. This species always floats on the water and spreads rapidly throughout the year.
  
  Compared to other breeds, this type of hyacinth is favored by environmental agencies because it does not "mat" as easily in the water. But, be aware that an overgrowth of any species of hyacinth plant produces a thick, entwined mass of roots that clog small waterways and suppresses animal life.
  
  

Anchored Water Hyacinth

• The U.S. Federal government bans the distribution or planting of the anchored water hyacinth (Eichhornia azurea) species. The Center for Invasive Species and Ecosystem Health (Invasive.org) says the anchored hyacinth resembles its cousin, the common hyacinth, except for a distinct yellow spot on each flower's top petal. Rather than float freely on the water, it roots itself to the bottom of shallow waterways.
  
  Once it anchors, it quickly reproduces and dominates the pond or stream. The overgrowth blocks sun from the water and suffocates aquatic life. The anchored water hyacinth can stop the flow of water in a small stream or river, and get tangled in boat motors.
  
  

Variable-Leaf Water Hyacinth

• Variable-leaf hyacinth (Eichhornia diversifolia) is less common outside of its native South American habitat. Compared to their cousins, variable-leaf hyacinths are susceptible to fluctuating water temperature and chemical balance. The leaves and stems of the variable-leaf hyacinth turn black if the plant encounters unfavorable conditions; it must be tended carefully to last through the winter. This species displays a diversity of leaf shapes and sizes, including ovate leaves like the common and anchored species.