Species & plants
Hydrilla
Also known as: Hydrilla verticillata, water thyme
Hydrilla (Hydrilla verticillata) is the most damaging submerged aquatic invasive in the United States by total acreage affected. It is identified by whorls of 3–8 leaves around a central stem, sandpaper-rough leaf edges with visible teeth, and small white tubers on the roots. Hydrilla extends 1–4 inches per day under good conditions, reaches the surface from depths up to 25 ft, and reproduces from stem fragments as small as a quarter inch. Tubers in the sediment remain viable for 4+ years, which is why eradication is nearly impossible without a multi-year program. Federally listed as a noxious weed.
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Related terms
- Tuber bankThe reservoir of viable tubers in pond or lake sediment that allows hydrilla regrowth even after the visible plant is gone.
- Mechanical harvestingRemoval of aquatic vegetation by purpose-built barge with submerged cutter blades and conveyor for off-site disposal.
- FluridoneA systemic aquatic herbicide used for hydrilla, milfoil, and other submerged invasives at very low concentrations.
- Triploid grass carpSterile grass carp stocked at 5–15 fish per acre to graze hydrilla and other tender submerged vegetation.
Related articles
- Hydrilla vs. native eelgrass: how to tell them apartNative eelgrass is fish habitat. Hydrilla is an invasive that smothers it. Here's how to identify what's in your water before you start treatment.
- Aquatic invasive weeds in the United States: identification guideNine invasive aquatic plants cause the majority of waterway damage across the United States. Here's how to identify each one before treatment.