Range Overview: Established Across the Nation
Hydrilla (Hydrilla verticillata) is established in more than 30 U.S. states, Puerto Rico, and the U.S. Virgin Islands. It is most pervasive in the Southeast but has established beachheads in every region of the country. The species continues to expand its range through recreational boating and aquatic plant trade despite decades of eradication efforts. No state can consider itself immune from hydrilla introduction, and waterway managers in currently uninfested states should maintain active prevention and early detection programs.
Regional Distribution
Southeast (Highest Severity)
The Southeast is hydrilla's stronghold in North America. Florida has the most extensive hydrilla infestations — virtually every major lake, river, and canal system in the state has been affected, with active infestations in Lake Okeechobee, the Kissimmee chain of lakes, St. Johns River, and hundreds of smaller water bodies. Georgia, South Carolina, North Carolina, and Alabama all have significant hydrilla infestations, particularly in major reservoirs (Lake Guntersville, AL; Santee Cooper, SC; Lake Murray, SC; Badin Lake, NC). The warm climate of the Southeast allows year-round hydrilla growth in southern portions, dramatically increasing its competitive advantage over winter-dormant native species.
Mid-Atlantic and Upper South
Virginia and Maryland have established hydrilla populations, most notably in the tidal Potomac River, where hydrilla became a major management issue starting in the 1980s and has required ongoing management ever since. Tennessee has infestations in several TVA reservoirs. Texas has scattered infestations in rivers and reservoirs, with the Colorado River system and several state park lakes infested. Arkansas and Mississippi have documented occurrences.
Northeast
Connecticut, New York, New Jersey, Delaware, and Pennsylvania all have documented hydrilla occurrences. The Northeast is colonized primarily by the dioecious biotype, which arrived from eastern spread of the southeastern population. Several lakes in Connecticut have active management programs. New York's Hudson River and several Long Island water bodies are infested. Spread in the Northeast is ongoing and concerning because the high density of recreational boating facilitates rapid dispersal among the region's many interconnected lakes.
Pacific States: The Monoecious Biotype
The Pacific Northwest harbors a genetically distinct monoecious biotype of hydrilla that spread independently from the dioecious southeastern population. Washington state has infestations in several lakes and canals in the eastern part of the state, most notably in irrigation water delivery canals in the Columbia Basin where hydrilla threatens water delivery infrastructure. Oregon has confirmed occurrences. California has had hydrilla infestations in irrigation canals and has invested heavily in eradication of detected populations.
Interior States
Hydrilla has been detected in scattered interior states including Missouri, Kansas, Indiana, Ohio, and others. These occurrences are typically isolated, often associated with aquarium releases or bait bucket dumping, and some states have achieved eradication of early infestations through rapid response. The Great Lakes basin states consider hydrilla one of the highest-priority aquatic invasive plant prevention targets.
How Hydrilla Spreads
The primary vector for hydrilla spread between water bodies is recreational boating. Hydrilla fragments and turions attach to boat hulls, propellers, live wells, bilge compartments, and trailers. When boats are moved from infested to uninfested waters without decontamination, these propagules are introduced to new systems. A single contaminated boat can introduce hundreds of viable hydrilla fragments to a new lake. Secondary vectors include: waterfowl (turions and fragments in gut, on feathers); moving water (flooding events connecting water bodies); and aquatic plant trade (hydrilla sold mislabeled as native ornamentals through some retailers, though this is illegal).
States with Active Eradication Programs
Several states have achieved significant management progress through sustained eradication programs: California has repeatedly achieved eradication of new canal infestations through early detection and rapid herbicide response. Some northeastern states have successfully eradicated isolated lake infestations detected early before large tuber banks established. The lesson from successful eradications is consistent — early detection and rapid response before tuber bank establishment are the keys to any realistic eradication outcome. Once a multi-year infestation is established with a full tuber bank, eradication transitions from feasible to effectively impossible, and management shifts to long-term population suppression.
Range Maps and Current Data
The most current hydrilla distribution data for the United States is maintained by the USDA APHIS National Invasive Species Information Center and the EDDMapS (Early Detection and Distribution Mapping System) database, maintained by the University of Georgia Center for Invasive Species and Ecosystem Health. State departments of natural resources also maintain state-specific occurrence databases. For management planning purposes, always consult your state agency's current occurrence data rather than historical records, as both new infestations and successful local eradications continuously update the effective range. See also our regional distribution hub for guides by state and region.
References
- EDDMapS. (2025). Early Detection & Distribution Mapping System. The University of Georgia, Center for Invasive Species and Ecosystem Health. eddmaps.org
- USDA NRCS PLANTS Database. Hydrilla verticillata. plants.usda.gov
- Thayer, D.D., et al. (2008). Hydrilla management in Florida. UF/IFAS Extension Circular 1089.