Pontederia crassipes

Lore & Background

Water hyacinth reproduces primarily by runners or stolons, forming daughter plants, and each plant can produce thousands of seeds annually that remain viable for over 28 years. Mats can double in size in one to two weeks, and in terms of plant count, they can multiply more than a hundredfold in 23 days. In its native range, flowers are pollinated by long-tongued bees, and the plant is tristylous, with three flower morphs based on pistil length: long (L), medium (M), and short (S). However, in introduced ranges, the M-morph prevails, the L-morph occurs occasionally, and the S-morph is absent, indicating founder events in its spread.

Anecdotally known as the 'terror of Bengal' due to its invasive growth, water hyacinth has been widely introduced in North America, Europe, Asia, Australia, Africa, and New Zealand. In New Zealand, it is listed on the National Pest Plant Accord, preventing propagation, distribution, or sale. It has become a serious pest in large water areas such as Louisiana, the Kerala Backwaters in India, Tonlé Sap in Cambodia, and Lake Victoria, where it was introduced in the 1980s. A 1.22 Gb/8 chromosome reference genome study suggests the spread of a limited genotype from South America, possibly originating from ships travelling from Itajaí Port on the Brazilian East Coast, though genetic studies from Bangladesh and Indonesia indicate different genotypes, implying multiple introduction vectors.

Reader's Guide

Water hyacinth is significant as a pernicious invasive species that grows and reproduces quickly, covering large portions of ponds and lakes. It outcompetes native aquatic plants, both floating and submerged, and can affect the photosynthesis of phytoplankton, submerged plants, and algae. Its decay depletes dissolved oxygen, often killing fish. It can absorb heavy metals but after death causes secondary pollution, destroying natural water quality and potentially affecting drinking water. Dense mats provide breeding places for disease vectors like mosquitoes and snails, posing health risks. Socioeconomically, its high evapotranspiration rate can dry out small lakes, leaving communities without adequate water or food supply. Mats prevent waterway use, leading to loss of transportation and fishing. Mechanical harvesting requires considerable effort: a million tons of fresh biomass would need 75 trucks of 40 m³ capacity per day for 365 days, and decomposition releases CO2, methane, and nitrogen oxides. The plant can also provide food for goldfish, keep water clean, and help with oxygenation. Invertebrate species harboring with water hyacinth are dispersed as phytochores. Genomic studies reveal adaptations in plant-pathogen interaction, plant-hormone signal transduction, photosynthesis, and abiotic stress tolerance, enabling niche expansion.

Did You Know?

• Its seeds can remain viable for more than 28 years.
• In its introduced range, the medium-pistil (M) flower morph prevails, while the short-pistil (S) morph is absent.
• Fresh plants contain prickly crystals and may induce itching.