Aquatic Weed Glossary
Aquatic Weed
Any aquatic plant — native or non-native — that grows in sufficient density or in a location where it causes economic, ecological, or recreational harm.
Emergent Plant
An aquatic plant that is rooted in submerged or saturated sediment with stems and leaves extending above the water surface. Examples: cattails, phragmites, bulrush.
The process by which a body of water becomes enriched in dissolved nutrients (especially phosphorus and nitrogen), stimulating excessive growth of aquatic plants and algae.
Floating Plant
An aquatic plant that floats on the water surface, with roots hanging freely in the water and leaves or stems above the surface. Examples: water hyacinth, duckweed, salvinia.
Fragmentation
A form of vegetative reproduction in which a plant fragment (stem, leaf, or root) detaches from the parent plant and establishes a new individual. The primary dispersal mechanism for many invasive submerged plants.
Herbicide
A chemical compound used to control plant growth. Aquatic herbicides are EPA-registered products specifically formulated and approved for use in aquatic environments.
Hypoxia
A condition of low dissolved oxygen in water, often caused by the decomposition of large biomass of aquatic plants. Can suffocate fish and other aquatic organisms.
Integrated Pest Management (IPM)
An ecosystem-based strategy for managing pests that combines multiple control methods — biological, mechanical, chemical, and cultural — to achieve long-term suppression with minimal environmental impact.
Invasive Species
A non-native species that has been introduced outside its natural range and causes economic, environmental, or human health harm. Not all non-native species are invasive.
Littoral Zone
The shallow nearshore zone of a lake or pond where sunlight reaches the bottom and aquatic plants can grow. The zone most heavily affected by aquatic weeds.
Monoculture
A plant community dominated by a single species to the exclusion of other species. Dense invasive aquatic weed growth often creates monocultures that dramatically reduce biodiversity.
Noxious Weed
A plant legally designated as harmful to agriculture, ecosystems, or human health by a government authority (federal or state). Noxious weed designation often restricts sale, transport, and propagation.
Submerged Plant
An aquatic plant that grows entirely beneath the water surface, rooted in sediment or free-floating. Examples: hydrilla, Eurasian watermilfoil, elodea, coontail.
A compact, dormant vegetative bud produced by some aquatic plants (notably hydrilla, duckweed) that sinks to the sediment and overwinters, germinating in spring. An important reproductive and survival strategy.
Tuber
An underground storage organ produced by some aquatic plants (notably hydrilla) that stores energy and serves as a long-lived propagule in the sediment. Tubers can remain viable for years.
Vegetative Reproduction
Asexual reproduction in which new plants arise from plant parts rather than from seeds. Includes fragmentation, stolons, rhizomes, turions, and tubers. The primary reproduction mode for most problematic aquatic weeds.
Alum Treatment
Application of aluminum sulfate (alum) to a lake to precipitate dissolved phosphorus from the water column and bind it to sediment, reducing internal nutrient loading. A widely used in-lake water quality restoration technique.
Aquatic Herbicide
An EPA-registered pesticide formulated and approved for use in aquatic environments. Aquatic herbicides differ from terrestrial products in formulation, label requirements, water use restrictions, and regulatory requirements. Only EPA-registered aquatic herbicides may be legally applied to water bodies.
Benthic Barrier
A sheet of woven or non-woven fabric anchored to the lake bottom to exclude light and prevent aquatic plant growth in a defined area. Commonly used for swimming areas, dock clearings, and boat launch areas.
Biotype
A genetically distinct population within a species that differs in ecologically relevant traits (herbicide tolerance, temperature range, growth form). Hydrilla has two biotypes (monoecious and dioecious) with different distributions and management implications.
Clean, Drain, Dry
The standard prevention protocol for aquatic invasive species: remove all plant material from boats and gear before leaving a water body (Clean); drain all water at the launch (Drain); and dry equipment for at least 5 days before entering a new water body (Dry).
Contact Herbicide
A herbicide that kills plant tissue it directly contacts without translocating through the plant. Effective against annual plants and algae; less effective against perennials with extensive root systems. Diquat is a widely used contact aquatic herbicide.
Cultural Eutrophication
Eutrophication driven by human activities (agriculture, urbanization, septic systems) rather than natural processes. Cultural eutrophication occurs on a timescale of years to decades, far faster than natural lake aging processes.
Dioecious
Having separate male and female plants. The dioecious biotype of hydrilla (found primarily in the southeastern U.S.) produces male and female flowers on different individual plants.
Dissolved Oxygen (DO)
Oxygen dissolved in water, measured in milligrams per liter (mg/L) or percent saturation. Essential for aquatic animal survival. Dense aquatic weed growth can cause nighttime DO crashes (below 2 mg/L) that cause fish kills in heavily vegetated ponds and lakes.
Drawdown
Intentional lowering of a lake or pond water level to expose shallow-water vegetation to freezing temperatures, desiccation, or ultraviolet radiation. Used as a non-chemical management technique for some aquatic plant species.
Fluridone
A systemic aquatic herbicide (carotenoid biosynthesis inhibitor) used for whole-lake management of hydrilla, Eurasian milfoil, and other submerged and floating weeds. Acts slowly (4–8 weeks) at low concentrations maintained over time.
Grass Carp
A large herbivorous fish (Ctenopharyngodon idella) native to Asia, used as a biological control agent for aquatic vegetation. Only triploid (sterile) grass carp are legally stocked in most U.S. states. Grass carp consume both invasive and native vegetation and cannot be species-selective.
Hydroperiod
The duration and seasonal pattern of inundation in a wetland or seasonal water body. Hydroperiod determines which plant and animal species can inhabit a wetland and is a key factor in invasive plant management strategy.
Internal Loading
Release of phosphorus from lake sediments into the water column, often triggered by low dissolved oxygen conditions in bottom waters. Internal loading can sustain eutrophication for years to decades after external nutrient inputs are reduced.
Macrophyte
Aquatic macrophyte: any large (visible to the naked eye) aquatic plant, as opposed to microscopic algae. Includes all submerged, floating, and emergent vascular plants as well as large algae like Chara. Macrophyte management is the scientific term for what is commonly called aquatic weed management.
Monoecious
Having both male and female flowers on the same plant. The monoecious biotype of hydrilla (introduced separately from the dioecious biotype and now found in the northeastern U.S. and expanding range) can reproduce sexually without a partner plant.
NPDES Permit
National Pollutant Discharge Elimination System permit, required under the Clean Water Act for discharge of pollutants (including aquatic pesticides) to waters of the United States. Aquatic herbicide applications to navigable waters may require NPDES permit compliance in addition to state aquatic plant management permits.
Point-Intercept Survey
A quantitative aquatic plant survey method in which plant presence, absence, and cover are recorded at systematically spaced grid points throughout a water body. Produces repeatable, comparable data for tracking management progress over time.
Rhizome
A horizontal underground stem that grows through sediment and produces new above-ground shoots at nodes. The primary vegetative spread mechanism for emergent aquatic weeds (cattails, Phragmites, alligator weed). Rhizome networks can spread 1–3 meters per year, and must be killed (not just cut) for effective control.
Stolon
A horizontal above-ground stem that grows across the water or sediment surface, producing new plants at nodes. The primary lateral spread mechanism for water hyacinth and other surface-spreading floating plants.
Systemic Herbicide
A herbicide absorbed by plant leaves or stems and translocated throughout the plant to roots and growing points, killing the entire plant including underground storage organs. Examples include fluridone, triclopyr, and imazamox. Preferred over contact herbicides for managing perennial plants with extensive root systems.
Water Use Restriction (WUR)
A period after aquatic herbicide application during which the treated water body cannot be used for specified purposes (drinking, irrigation, swimming, fish consumption). WURs are specified on the product label and vary by active ingredient, concentration, and intended use. All water body users must be notified of applicable WURs before treatment.