HORNED PONDWEED 



Zannichellia palustris L. 



Horned pondweed is a cosmopolitan plant that is classified in a 

 different plant genus than the other aquatic weeds referred to as 

 pondweeds. The Zannichellia genus has one species only. This plant 

 resembles sago pondweed, but upon close examination many 

 differences can be noted. Leaves of horned pondweed are much 

 narrower and threadlike and arranged on the stems in an opposite 

 manner, while those of sago pondweed develop from the stems in an 

 alternate pattern. This is a completely submersed plant that develops 

 a dense, creeping system of horizontal stems that are shallow rooted 

 with sparsely branching stems. It produces a dense, usually short, mass 

 of vegetation. 



The plant derives its common name from the incurving hornlike 

 beaked fruits (insert 1) which are usually found in threes or fours with 

 very short fruit stems (peduncles). Flowers and fruits are produced in 

 the axils of the leaves (insert 2). Unlike true pondweeds of the 

 Potamogeton genus, this plant does not produce vegetative 

 overwintering structures and is carried through adverse growing 

 conditions and disseminated by seed. 



Horned pondweed is a widespread aquatic weed and can most often 

 be observed in spring or early summer, preceding the growth of other 

 more vigorous pondweeds, although it will grow in association with the 

 true pondweeds. Horned pondweed is rather unique in that it will 

 tolerate excessively cold water and can often be seen growing as small 

 tufts on the bottom of streams and canals of Northern latitudes during 

 winter months. 



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