Family: Pontederiaceae
An invasive herbaceous plant. Native to the Neotropics, water hyacinth was introduced to Hawaiʻi by E.W. Jordan in the latter part of the 1800s. Populations are established on Kauaʻi, Oahu, Maui, and Hawaiʻi. DO NOT introduce this plant to slow-moving or stagnant waterways. The Division of Forestry and Wildlife of the Hawaiʻi Department of Land and Natural Resources has designated this species as one of Hawaiʻi’s Most Invasive Horticultural Plants. It is considered one of the worst aquatic weeds in the world.
Description and Dispersal:
- A floating herbaceous plant
- Round,leathery,shiny leaves
- Dark roots
- Fleshy stems with spongy/starchy stalks
- 1 inch to 3 feet in height
- Showy purple (sometimes white) flowers with 6 petals
- Fruit is a three celled capsule containing many minute seeds
- Reproduces vegetatively from fragments
- Seeds are water,wind, bird and human dispersed
High Risk Traits:
- Naturalized beyond native range (e.g., Hawaii).
- Agricultural weed (e.g., damages rice & fish production).
- Environmental weed (degrades aquatic habitats, displaces natives).
- Congeneric weed (other species are invasive).
- Broad climate suitability (tolerates wide temperature range).
- Unpalatable to most grazing animals.
- Shade tolerant (outcompetes submerged plants).
- Forms dense, floating mats.
- Reproduces rapidly via vegetative fragmentation.
- Self-compatible (can self-pollinate).
- Reaches reproductive maturity quickly (~1 year).
- Dispersed intentionally and unintentionally by people.
- Dispersed by water and birds (seeds on feet).
- Forms a persistent seed bank (seeds viable for years).
- Tolerates mutilation (fragmentation aids spread).
Low Risk Traits:
- Lacks spines, thorns, or burrs.
- Not toxic to animals or humans.
- Does not create a fire hazard.
- Not adapted for wind dispersal.
- Effectively controlled by specific herbicides (e.g., glyphosate).
- Biological control agents exist and are effective.
