DUCKWEED 



Lemna spp. and Wolffia spp. 



Duckweeds are characterized by their diminutive size and lack of 

 stems and true leaves. They are the simplest and some of them the 

 smallest of flowering plants. Duckweeds are free-floating on or slightly 

 beneath the water surface. The plant consists of a leaflike structure, 

 or frond, and in some species a single root that penetrates into the 

 water. The flowers, being inconspicuous and simple in structural form, 

 arise from the edge or upper surface of the fronds. These are seldom 

 seen and some species apparently never flower. 



This family of plants has four genera, of which Lemna is probably 

 most often seen on irrigation systems where water is static. A typical 

 vegetative habitat of this species is shown, consisting of hundreds of 

 plants covering the surface of very slow moving or quiet waters. Lemna 

 minor L., as illustrated, is one of the smaller species. A single frond 

 of this plant is about the size of a pinhead. Plants of the Wolffia gtnxis 

 have fronds much smaller than Lemna and are microscopic in size. 

 They can be detected by the greenish cast they impart to the water 

 surface. Plants in this family propagate vegetatively by proliferous 

 growth of new individuals from the edge or base of the parent fronds. 

 During warm summer months these plants can cover the surface of 

 a pond in a few weeks. The plant overwinters both by seed and 

 vegetatively by a minute bulblet frond that sinks to the bottom of the 

 water body and rises to the surface the following season. 



These plants become pests to irrigation systems when they are 

 carried into siphon tubes, trashracks, and pump inlet structures from 

 their still water habitat. 



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