“Beautiful but deadly” are terms that apply describe water hyacinth (Eichhornia crassipes). Most people, particularly southerners, will quickly recognize the plant. That is how widespread it has become. Massive floating mats of green and when in bloom the lush bluish purple flowers present quite a spectacle. Water hyacinth is a non-native invasive species. Native to tropical and subtropical South America, it has been widely introduced in North America and many other countries as decorative plants for garden ponds from where it escaped. It is one of the most productive plants on earth and is considered perhaps the worlds most pernicious aquatic plant. When not controlled, it will literally cover every inch of ponds and even large lakes. Millions are spent each year to combat the spread water hyacinth, generally to little avail.
The story goes that water hyacinth was introduced into the United States in 1884 at the Worlds Fair in New Orleans, also known as the World Cotton Centennial. Apparently the plants were being given away as gifts by a group of visiting Japanese. From this humble start, water hyacinth quickly spread through the southeast west and north to somewhat cooler climates. Being cold sensitive, it is unable to survive in temperatures much below 45-50 degrees F. Nor does it tolerate water temperatures above 90 degrees F. With an optimum growth temperature of 77-85 degrees F, the SE U.S. west into Texas is prime habitat. The roots hang down into the water column and absorb nutrients sufficient for growth which is augmented by its rapid photosynthetic rates. The plant reproduces vegetatively by way of runners which quickly form daughter plants. Each mature plant produces thousands of seeds every year that can remain viable for 25-30 years. One study showed that two plants produced 1200 daughter plants vegetatively in four months and as many as 10,000 seeds in a year which waterfowl eat and subsequently disperse. It’s no wonder it has spread so widely.
I remember as a boy growing up in the south Louisiana marshes and swamps how much effort was expended just to fight water hyacinth back lest the ever spreading mats of vegetation choke off navigation through the waterways. These mats get so thick they stop sunlight from reaching the water column dramatically reducing fish populations and aquatic food chains in general. Water Hyacinth does not tolerate salt so rarely moves into brackish salt marshes (thankfully). We used to watch as boats sprayed toxic herbicides on the thick floating mats. This was long before the days of EPA. I often wondered, if it kills the plant what is it doing to the fish and other organisms? As the plants died they had to be raked up on the banks or the volume of dead vegetation that sank to the bottom decayed and used all the oxygen on large sections of waterways. Summer fish kills often resulted. It was not a pretty sight. We used to walk on the swollen stem “floats” piled up on the banks just to hear them pop. Remember, in the 50’s we did not have computers, cell phones, smart phones, game boys, walk man, etc, etc. Life was a lot simpler back then. So, enjoy the beauty of the flowers because that is probably the only benefit we receive for having water hyacinth in this Country.