Cornell Cooperative Extension

Cayuga County

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).  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 which are often spread unknowingly by humans and animals or by someone dumping an aquarium irresponsibly.

Bloom of cyanobacteria ("blue-green algae"). traces shaped streaks are traces of fish and ducks that run on water, "breaking" the biofilm. The samples emit a strong odor of algae (spirulina type). Location: "Quai du Wault" in Lille, not far from downtown (north of France; Location vai google maps: 50.637485,3.05425)

Blue-Green Algae

Studies have linked invasive hydrilla to a deadly toxin produced by blue-green algae, resulting in illness and death of wild birds and domestic pets.

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How to Identify Hydrilla

Hydrilla can be identified by many characteristics, such as pointed leaves, potato-like tubers, and aggressive growth.

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Last updated May 30, 2023

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 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.