Hydrilla & egeria

Hydrilla verticillata

The Hydrilla (Hydrilla verticillata) may have been introduced to North

America in Florida during the 1950′s. This aggressive, invasive species and has spread throughout Florida and most southern states, as well as California, Delaware, and the District of Columbia. Hydrilla has been categorized as one of the world’s worst weeds, and it is certainly among the most notorious of submerged aquatic plant species. Infestations of Hydrilla are extremely severe and can completely choke entire lakes and public water supplies.

Submersed perennial herb. Rooted, with long stems that branch at the surface where growth becomes horizontal and dense mats form. Small, pointed leaves are arranged in whorls of 4 to 8. Leaves have serrated margins and one or more sharp teeth under the midrib (Godfrey and Wooten 1979). Development of these features may vary with location, age, and water quality (Kay 1992).

Dense mats alter water quality by raising pH, decreasing oxygen under the mats, and increasing water temperature. Stagnant water created by hydrilla mats provides good breeding grounds for mosquitos. Hydrilla interferes with recreational activities such as swimming, boating and fishing. In eastern Washington, hydrilla has the potential to impact power generation and irrigation by clogging dam trash pipes and intake pipes.