Aquatic weed glossary
Plain-English definitions of aquatic invasive species, remediation methods, herbicides, regulations, and biology. Written for Florida lakefront owners, HOAs, and pond operators — but applicable across the United States.
Species & plants
Hydrilla
Hydrilla verticillata, water thymeA submerged invasive aquatic plant that grows in dense canopy mats and persists through tubers in the sediment.
Water hyacinth
Eichhornia crassipes, Pontederia crassipesA free-floating invasive plant with bulbous petioles and showy purple flowers, capable of doubling in 8–12 days.
Water lettuce
Pistia stratiotesA free-floating rosette invasive that resembles a head of romaine lettuce on the water surface.
Eurasian watermilfoil
Myriophyllum spicatum, milfoilA submerged invasive with feather-like leaves in whorls of 4, dominant across northern US lakes.
Eelgrass (Vallisneria)
Vallisneria americana, tape grass, wild celeryA native submerged plant that provides primary fish habitat and is often confused with hydrilla.
Cattail
Typha latifolia, Typha domingensisA native emergent wetland plant that spreads by underground rhizomes and aggressively colonizes shorelines.
Alligator weed
Alternanthera philoxeroidesA mat-forming invasive with hollow jointed stems and a single white clover-like flower at each leaf axil.
Giant salvinia
Salvinia molestaA free-floating fern with paired oval leaves and diagnostic egg-beater hairs; one of the worst invasives globally.
Duckweed
Lemna minorTiny free-floating native plant 2–5 mm across with a single root; can double in 2 days under high nutrients.
Watermeal
WolffiaThe smallest flowering plant in the world; rootless, under 1 mm, looks like green grit on the water surface.
Filamentous algae
pond scum, string algaeBright green stringy mats of single-celled algae that bloom on nutrient-loaded ponds in warm weather.
Cyanobacteria
blue-green algae, harmful algal bloom, HABPhotosynthetic bacteria that produce toxic blooms; not true algae despite the common name.
Parrot feather
Myriophyllum aquaticumAn invasive milfoil with feathery emergent foliage above the waterline; often escapes from water gardens.
Methods & equipment
Mechanical harvesting
Removal of aquatic vegetation by purpose-built barge with submerged cutter blades and conveyor for off-site disposal.
Hydraulic dredging
Pumping water and sediment through a cutter head and pipe to remove vegetation, muck, and the seed bank in one pass.
Drawdown
Lowering pond or reservoir water levels in fall or winter to expose vegetation to freezing and dehydration.
Biological control
biocontrolThe deliberate introduction of organisms — fish, insects, fungi — that consume specific invasive plants.
Triploid grass carp
sterile grass carp, white amurSterile grass carp stocked at 5–15 fish per acre to graze hydrilla and other tender submerged vegetation.
Benthic barrier
A physical mat laid on the lake bottom to block sunlight and prevent rooted aquatic plant growth.
Shoreline boom
containment boomA floating barrier deployed along a shoreline to catch drifting floating vegetation before it reaches docks.
Chemistry & herbicides
Aquatic herbicide
Any EPA-registered herbicide labeled for application to standing water or aquatic vegetation.
Fluridone
A systemic aquatic herbicide used for hydrilla, milfoil, and other submerged invasives at very low concentrations.
Glyphosate
Rodeo, AquaMasterA non-selective systemic herbicide used for emergent and floating aquatic vegetation.
2,4-D
A selective broadleaf herbicide used for water hyacinth, water lettuce, and Eurasian watermilfoil.
Endothall
A contact aquatic herbicide for hydrilla, pondweeds, and milfoil; faster-acting than fluridone.
Imazapyr
A long-residual selective herbicide for shoreline emergents; persists in soil for 6+ months.
Diquat
A fast-acting contact herbicide for floating and submerged aquatic plants.
Copper sulfate
chelated copper, copper algaecideA copper-based algaecide that kills filamentous algae and cyanobacteria on contact.
Biology & ecology
Tuber bank
The reservoir of viable tubers in pond or lake sediment that allows hydrilla regrowth even after the visible plant is gone.
Rhizome
An underground horizontal stem that produces shoots and roots; the main reproductive structure of cattails and many emergents.
Doubling time
The time required for an aquatic plant population to double in biomass under given conditions.
Fragmentation
Asexual reproduction by plant fragments breaking off and rooting as new plants.
Eutrophication
The over-enrichment of a water body with nutrients, leading to chronic algae blooms and oxygen crashes.
Phosphorus loading
The rate of phosphorus inputs to a water body; the limiting nutrient for most freshwater algae blooms.
Dissolved oxygen
DOThe concentration of oxygen dissolved in water, expressed in mg/L; the variable that controls fish survival.
Littoral zone
The shoreline region of a lake where sunlight reaches the bottom and rooted aquatic plants grow.
Regulations & permits
FWC
Florida Fish and Wildlife Conservation CommissionThe Florida agency that manages aquatic plant control on public waters and licenses commercial applicators.
Water Management District
WMD, SJRWMD, SWFWMD, SFWMDFlorida's regional regulatory bodies that permit shoreline alteration in regulated wetlands.
Environmental Resource Permit
ERPFlorida permit required for shoreline alteration, dredging, and wetland-vegetation removal in regulated waters.
Outstanding Florida Waters
OFWA designation of Florida water bodies given heightened protection; many spring-fed rivers and natural lakes are listed.
Aquatic plant permit
A Florida permit (FWC or WMD) required for transport of prohibited aquatic plants and certain shoreline alterations.
Riparian rights
The common-law right of waterfront property owners to reasonable use of the adjacent water, including dock-access vegetation removal.
FDACS
Florida Department of Agriculture and Consumer ServicesThe Florida agency that licenses pesticide and herbicide applicators, including aquatic pest control category.
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