AMERICAN PONDWEED 



Potamogeton nodosus Poir. 



American pondweed is commonly found growing near the 

 shoreline of lakes and ponds. Its presence becomes very obvious by the 

 extensive development of floating leaves in midsummer. Its specific 

 name, nodosus, inferring knotty, is a description apparently derived 

 from the slight swelling at each stem-joint, or node, giving the plant 

 stem a slight knotty appearance. This species infests laterals with 

 low-velocity waters and the shallow areas of lakes, reservoirs, and ponds. 

 This pondweed, although cosmopolitan in distribution, is most 

 frequently found growing in irrigation laterals or in slow-moving water. 



The mature plant produces both submersed and emersed leaves. 

 The submersed leaves are thin membranous structures that are long, 

 narrow, and taper into the stem without a well-developed petiole (leaf 

 stem). The mature submersed leaf is usually brownish-red in color but 

 may, in deeper water, be more of a light green. 



Emersed or floating leaves are narrow-elliptical in shape, firm, and 

 possess a definite waxy cuticle on the upper surface. Flowers are borne 

 on a compact spike that emerges above the water surface for wind or 

 insect pollination. Following development of the beaked nutlike fruit 

 (insert 1 ), the spike turns down to submerse the maturing fruit head. 

 The species spreads and is reproduced in subsequent seasons by long, 

 slender buds that develop in chains on the terminals of horizontal 

 stems (insert 2). Like sago pondweed, these vegetative winter-buds are 

 produced in great numbers at depths of 0.05 to 0.30 meter below the 

 surface of the aquatic soil. The winter-bud is easily distinguished from 

 the terminal shoot buds by its makeup of overlapping fleshy scales. 



In growth habit, American pondweed resembles one or two other 

 species of pondweeds. Differentiation can often be made only by the 

 use of detailed botanical references. 



