WHITESTEM PONDWEED 



Potamogeton praelongus Wulfen 



Whitestem pondweed, or praelongusas it is often called, is usually 

 found in deep, cold water of clear lakes or irrigation conveyance 

 systems near such water sources. It undoubtedly will be found more 

 often in deeper canals, but has seldom been reported as a serious 

 aquatic pest. The similarity of this species to a number of other 

 pondweed species can be confusing to an identifier without 

 examination for specific growth character. 



The large white or whitish stem that quite often grows in a zigzag 

 pattern is distinctive (insert 1). Leaves of this species are oval to linear 

 and are similar to Richardson pondweed in growth pattern, except that 

 praelongusis generally larger and produces leaves with broad bases that 

 never clasp the stem more than halfway. All leaves are submersed and 

 become progressively shorter toward the tip of a branch. The tips of 

 the leaves are boat shaped. The plant is produced from stoutish white 

 rhizomes that are covered with rusty spots. 



Flowers and the strongly beaked nutlike fruits are produced on a 

 spike that emerges above the water surface. 



This species is widespread across the northern part of North 

 America and has been reported primarily from streams and lakes in 

 the Pacific Northwest. 



12 



