WATERWEED 



Elodea canadensis Michx. 



This completely submersed plant is often seen growing in dense 

 patches in all types of freshwater habitats. It is commonly referred to 

 as waterweed, water-thyme, or ditch-moss. Also, the generic name 

 Elodea, a derivation of the Greek e/oc/e^ (meaning marshy), is 

 becoming an increasingly popular name for plants in this genus. 

 Anarcharis and Philotn'a are synonymous names for this plant genus 

 that are falling into disuse. The plant is probably an escapee from 

 ornamental culture in aquariums. 



There are a number of species of this genus, but E . canadensis is 

 the most widespread in irrigation waters. The vegetative growth habit 

 is distinct, making identification of the genus quite easy. Species 

 identification becomes more laborious but does not require detailed 

 study. The slender stems branch readily into paired forks with whorls 

 of leaves three or four in number at each stem node. Individual leaf 

 bases are somewhat clasping, forming a continuous ring around the 

 stem (insert 1). Leaf margins are small toothed. Male and female 

 flowers are borne on separate plants. The pistillate or female plant is 

 the one seen most often, producing leaf whorls that are more dense 

 with shorter stem intemodes than those on the male plant. 



The waterweed flower is produced quite often on the end of 

 threadlike shoots that grow to the water surface. Fruits and seeds are 

 rare because of the scarcity of male plants. Dissemination of the plant 

 is from vegetative buds produced on the terminal ends of shoots and 

 by plant fragmentation. The plant overwinters by these vegetative 

 buds that break from the stems in late summer and fall into the bottom 

 mud (insert 2). This plant will survive and grow in a completely floating 

 state, although it usually grows much more vigorously when rooted in 

 soil. 



Waterweed is very common to practically all areas of Western 

 irrigation systems and can be found growing in patches in both large 

 canals and small laterals. It will produce very dense stands in 

 slow-moving water of canals and shallow areas of reservoirs and ponds. 



