A Native Aquatic Plant That Can Become a Nuisance
Coontail (Ceratophyllum demersum), also known as hornwort, is one of the most common submerged aquatic plants in North America and across much of the world. Unlike hydrilla, Eurasian watermilfoil, and curly-leaf pondweed — the major invasive submerged weeds — coontail is native to North American water bodies. It is an important ecological component of many lakes, rivers, and wetlands, providing fish habitat, waterfowl food, and invertebrate cover. Yet coontail can also reach nuisance densities in eutrophic water bodies, forming dense mats that obstruct navigation, recreational use, and sometimes displace the more diverse native plant communities it is supposed to be part of.
This native/nuisance dichotomy is the essential context for all coontail management decisions. Management of coontail is typically only warranted when it has reached densities that cause meaningful ecological or recreational harm, and management approaches should be carefully calibrated to suppress nuisance growth without eliminating the ecological benefits the plant provides at lower densities. Treatment regulations and management philosophy for coontail differ markedly from those for non-native invasive species.
Taxonomy and Distribution
Coontail belongs to the family Ceratophyllaceae, with only one genus (Ceratophyllum) and approximately 6 species worldwide. Ceratophyllum demersum is the most common and widespread species in North America. It has a remarkable global distribution — it is found on every continent except Antarctica, in waters ranging from tropical to subarctic. In North America, it occurs across all contiguous states and most Canadian provinces, wherever fresh water exists.
Ceratophyllum echinatum (spiny hornwort or prickly hornwort) is a less common native North American species of coontail that occurs in some eastern and midwestern lakes. It is similar to common coontail but has spiny fruit and slightly different leaf texture. Management considerations are the same as for C. demersum.
Key Biology: A Rootless Plant
One of coontail's most distinctive biological features is the absence of true roots. Most aquatic plants anchor themselves in sediment with a root system. Coontail has no roots — it floats freely in the water column, anchored only by the weight of its dense branching stems and by contact with the sediment bottom. In shallow water, the bottom stems may contact sediment and absorb some nutrients through specialized root-hair-like structures at stem tips, but these are not true roots. Most nutrient acquisition occurs through the entire stem surface from the surrounding water.
This rootless architecture has implications for both ecology and management. Coontail can grow without anchoring to a substrate, which allows it to colonize areas with unstable sediment, hard bottoms, or moving water where rooted plants cannot establish. It is also highly mobile — dense coontail mats can be dislodged by wind and current and transported to new areas of a lake or downstream. From a management perspective, coontail cannot be controlled by sediment treatments that target rooted plants, and its removal by mechanical harvesting must account for the ability of free-floating fragments to re-establish downstream or in newly cleared areas.
Ecological Value
At appropriate densities, coontail provides significant ecological value:
- Fish habitat: Dense coontail beds provide essential structure for juvenile fish — cover from predators, shade, and habitat complexity. Largemouth bass, bluegill, crappie, and pike all use coontail beds extensively. Coontail beds in the 1–4 foot depth zone in northern lakes are particularly important for largemouth bass reproduction and juvenile survival.
- Waterfowl food: Seeds, plant tissue, and associated invertebrates are consumed by many duck and goose species. Redheads, canvasbacks, and other diving ducks eat coontail directly.
- Invertebrate habitat: The complex structure of coontail stems and leaves supports dense communities of aquatic invertebrates — midges, amphipods, water fleas, and snails — that serve as food for fish and waterfowl.
- Oxygen production: At moderate densities, coontail photosynthesizes and contributes to dissolved oxygen production in the water column.
For identification guidance that helps distinguish coontail from invasive hydrilla, see the coontail vs. hydrilla comparison guide.
References
- Les, D.H. (1988). Ceratophyllum systematics. Systematic Botany 13(3):359–388.
- Nichols, S.A. (1991). The interaction between biology and management of aquatic macrophytes. Aquatic Botany 41:225–252.
- USDA NRCS PLANTS Database. Ceratophyllum demersum. plants.usda.gov