Photo of water hyacinth flower in bloom, Clearwater, Florida (2014).
Eichhornia crassipes, commonly known as (common) water hyacinth, is an aquatic plant native to the Amazon basin, and is often considered a highly problematic invasive species outside its native range.
Water hyacinth is a free-floating perennial aquatic plant (or hydrophyte) native to tropical and sub-tropical South America. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in height. The leaves are 10–20 cm across, and float above the water surface. They have long, spongy and bulbous stalks. The feathery, freely hanging roots are purple-black. An erect stalk supports a single spike of 8-15 conspicuously attractive flowers, mostly lavender to pink in colour with six petals. When not in bloom, water hyacinth may be mistaken for frog’s-bit (Limnobium spongia).
One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. Each plant can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years. The common water hyacinth (Eichhornia crassipes) are vigorous growers known to double their population in two weeks.
ts habitat ranges from tropical desert to subtropical or warm temperate desert to rainforest zones. The temperature tolerance of the water hyacinth is the following; its minimum growth temperature is 12o C (54o F); its optimum growth temperature is 25-30o C (77-86o F); its maximum growth temperature is 33-35o C (92-95o F), and its pH tolerance is estimated at 5.0 to 7.5. It does not tolerate water temperatures >35 °C. Leaves are killed by frost and salt water, the latter trait being used to kill some of it by floating rafts of the cut weed to the sea. Water hyacinths do not grow when the average salinity is greater than 15% that of sea water. In brackish water, its leaves show epinasty and chlorosis, and eventually die.
Because of E. crassipes invasiveness, several biological control agents have been released to control it, including two weevils (Coleoptera: Curculionidae), Neochetina bruchi Hustache and Neochetina eichhorniae Warner, and the moth Niphograpta albiguttalis (Warren) (Lepidoptera: Pyralidae). Neochetina eichhorniae causes “a substantial reduction in water hyacinth production” (in Louisiana); it reduces plant height, weight, root length, and makes the plant produce fewer daughter plants. N. eichhorniae was introduced from Argentina to Florida in 1972.
Azotobacter chroococcum, an N-fixing bacteria, is probably concentrated around the bases of the petioles. But the bacteria do not fix nitrogen unless the plant is suffering extreme N-deficiency.
Fresh plants contain prickly crystals. This plant is reported to contain HCN, alkaloid, and triterpenoid, and may induce itching. Plants sprayed with 2,4-D may accumulate lethal doses of nitrates, as well as various other nocive elements in polluted environments. See further down.