Cornell Cooperative Extension

Monroe County
Hydrilla, Hydrilla verticillata
Image by Chris Evans, Bugwood.org

Hydrilla verticillata

About Hydrilla

Hydrilla was once used in aquariums for many of the same reasons it makes for such an invasive pest. It is extremely hardy and can grow in many conditions (including low light levels and poor nutrient areas). It's agressive spread put the local ecology and economy at risk.

Hydrilla was first found in the wild in Florida in the 1950s, believed to have escaped from the aquarium trade. It has since spread to many parts of the US. Hydrilla can spread quickly since fragments of the plant can sprout roots and establish new populations. Fragments are easily caught and transported by boats and boat trailers, and can be dispersed by wind and water currents. Hydrilla also reproduces and spreads by buds produced along the stems (probably spread by an unknowing or someone dumping an aquarium irresponsibly.


Last updated October 5, 2015

About Hydrilla

Aggressive Growth

Hydrilla grows aggressively, up to a foot a day (1). Early in the season, it grows horizontally along the bottom of the water body. Side shoots and new tubers can develop at the nodes as the plant grows. As the water temperature increases, the stems elongate, sending the shoot tips toward the water surface, creating a thick mat of vegetation. It quickly shades out other aquatic plants, displacing beneficial native species like pond weeds and wild celery.

Source: Center of Aquatic and Invasive Plants, University of Florida, IFAS

Federal Noxious Weed

Hydrilla verticillata is found on the USDA's Federal Noxious Weed List and is regulated by strict permits.

It is illegal to sell/buy hydrilla. However, many sales occur due to misidentification of the plant and/or contamination of legal sales.Since hydrilla looks very much like elodea, another commonly sold aquarium plant, people sometimes mistake one plant for the other and mislable hydrilla, or, a stray piece of hydrilla will get packed along with a shipment of elodea.

Quick Facts

  • Hydrilla is one of the world’s most invasive plants.
  • Can grow up to a foot a day.
  • Forms thick dense mats that block sunlight and kill native plants.
  • Reduces oxygen in the water and alters fish habitat.
  • Eliminates waterfowl feeding areas and fish spawning sites.
  • Obstructs boating,swimming, and fishing.
  • Lowers the value of waterfront property.
  • Blocks intakes at water treatment,power generation, and industrial facilities.
  • Clogs flood control channels.