Water Hyacinth Identification & Treatment
Scientific Name: Eichhornia crassipes Category: Floating Tier: 1 — High-Priority — Most prevalent and/or most damaging across the US
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Identification
Water hyacinth is a large, free-floating plant with thick, glossy, rounded leaves and distinctive swollen (bulbous) leaf stalks that act as floats. Plants can grow 1–3 feet above the water surface. Produces showy lavender-blue flower spikes. Long, feathery dark roots dangle below the plant into the water column. Key distinguishing features:
- Thick, rounded, glossy green leaves
- Swollen, spongy leaf stalks (petioles) filled with air
- Showy lavender-blue flowers with yellow markings
- Dark, feathery root mass hanging beneath plant
Commonly confused with: Water lettuce (lighter green, velvety texture, no flowers), frog's-bit (much smaller, heart-shaped leaves)
Treatment
Recommended Natural Waterscapes Products:
- Harvester (diquat) — Contact herbicide; fast knockdown of water hyacinth. Apply directly to foliage. Harvester
- Glyphosate 5.4 — Systemic herbicide for emergent/floating weeds. Apply to actively growing foliage. Most effective when plants are not stressed. Glyphosate 5.4
- Clearcast (imazamox) — Systemic herbicide effective on water hyacinth. Clearcast
Non-chemical: Physical removal (raking, skimming) for small infestations. Biological control using host-specific weevils (Neochetina spp.) has been successful in some regions as a long-term population management strategy.
Regional Note: Water hyacinth is winter-hardy only in USDA Zones 8–11. In Zones 7 and below, it is killed by freezing temperatures and is generally not a recurring management issue unless reintroduced. In southern states (Southeast, Gulf Coast, Southern Coastal Plain ecoregions), it is one of the most damaging aquatic invasive plants and can double its population in as little as two weeks during summer.
Full Profile
- Native Range: Amazon Basin, South America
- US Distribution: Primarily southeastern US — EPA Ecoregions: Southern Coastal Plain, Southeastern Plains, Mississippi Alluvial Plain, East Central Texas Plains, Western Gulf Coastal Plain. Found in portions of California, Arizona, and Hawaii. USDA Zones 8–11 (persistent); can appear temporarily in Zones 6–7 as an escapee from water gardens.
- Regulatory Status: Federal Noxious Weed (USDA APHIS). Prohibited in most southern and western states.
- Habitat: Still or slow-moving freshwater — ponds, lakes, rivers, canals, ditches. Thrives in warm, nutrient-rich water. Requires full sun.
- Reproduction: Primarily vegetative via stolons (runners). A single plant can produce 3,000 offspring in 50 days. Also produces seeds that can remain viable in sediment for 15–20 years.
- Ecological Benefits: In small amounts and in its native range, water hyacinth absorbs excess nutrients and heavy metals from water (used in some wastewater treatment applications). Provides habitat for invertebrates in root masses. However, dense infestations are overwhelmingly harmful — blocking light, depleting oxygen, impeding navigation, and destroying native plant communities.
- Seasonal Behavior: In frost-free areas, grows year-round. Killed by sustained freezing temperatures. Peak growth in summer months with warm water and long day length.
Sources: Texas A&M AquaPlant – Water Hyacinth | UF/IFAS EDIS | USDA APHIS Federal Noxious Weed List
Related Species
- Duckweed (Lemna minor and related species (L. gibba, L. turionifera, Spirodela polyrhiza)) — Floating, Tier 1
- Watermeal (Wolffia spp. (W. columbiana, W. brasiliensis)) — Floating, Tier 1
- Water Lettuce (Pistia stratiotes) — Floating, Tier 2
- Giant Salvinia (Salvinia molesta) — Floating, Tier 2
- European Frog's-bit (Hydrocharis morsus-ranae) — Floating, Tier 3
- Mosquito Fern (Azolla) (Azolla spp.) — Floating, Tier 3
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