The source of the infestation was a Maryland supplier of waterlilies. Apparently the hydrilla came in as a contaminant of waterlily shipments. Herbicide treatments were initiated on August 16. Eradication efforts are ongoing in Clear Lake. Geographical Distribution Hydrilla is native to parts of Asia, Africa, and Australia.
Hydrilla is found as far west as Texas and California.
Monoecious hydrilla is found in lakes in North Carolina and the Potomac River near Washington D.C. and also has been reported in Maryland and Delaware. The monoecious plants in Washington State represent the northernmost occurrence of hydrilla in the United States. Hydrilla is not known to occur in Oregon, Idaho, or British Columbia. These states and provinces are very concerned about the infestation in Washington and are pressing for responsible action on our part. Habitat Hydrilla is a submersed, freshwater perennial herb, generally rooted on the bottom in depths of greater to 20 feet where water clarity is good.