WATERCHESTNUT 43 



Detached, well-developed rosettes are capable of taking root on 

 muddy margins and maturing a crop of seeds. The plant is 

 strictly an annual, and the comparatively small number of seeds 

 produced, commonly a dozen or more, are its sole means of sur- 

 vival. Nevertheless, a small infestation located on the Potomac 

 near Alexandria, Va., in 1923 extended itself 35 miles in 15 years 

 — its beds blanketing much of the shallow water in this distance. 



IMPORTANCE 



Some use is made of the seeds as human food in Asia and 

 Europe, but in this country the plant appears to be wholly a lia- 

 bility. The "waterchestnut" served in American versions of Chi- 

 nese dishes is not Trapa natans but Eleocharis dulcis, an entirely 

 different plant. Dense beds of waterchestnut can impede or pre- 

 clude both commercial and recreational navigation, destroy use- 

 fulness of areas for bathing, fishing, and waterfowl hunting, and 

 increase hazards from malarial or nuisance mosquitoes. It is not 

 only a serious pest at present but also menaces waterways not 

 yet invaded. Once in a river system, its eradication is costly. 

 Control work on waterchestnut in the Potomac River required 

 more than 20 years of extensive operations costing several hun- 

 dred thousand dollars, and additional years of patrol and cleanup 

 activity will be necessary before extermination is complete. 



PRESENT EXTENT 



NEW YORK STATE: Waterchestnut is estimated to cover about 2,500 

 acres in the Hudson and Mohawk Rivers. It appears rather 

 hopelessly entrenched in these streams because danger to nearby 

 crops limits safe and effective control. The plant has been largely 

 or entirely eliminated in a number of small water areas near 

 these two streams, but meanwhile it has invaded Lakes Keuka 

 and Champlain. 



MASSACHUSEHS: Beds in or near the Sudbury and Concord Rivers are 

 reported to have been brought largely under control during the 

 past decade, but it will be years before the weed is entirely 

 eliminated here. An infestation in a pond on the Mount Holyoke 

 College campus at South Hadley is a threat to the Connecticut 

 River. 



VERMONT: Watcrchestnut was found on the Vermont side of Lake 

 Champlain's southern end in 1950, presumably introduced by 

 freight barges. Limited-scale control efforts are under way. 



