WATERMILFOIL 



Myriophyllum spp. 



Watermilfoil may be completely submersed with just the flowering 

 spikes emersing, or in certain species portions of the stem and leaves 

 may be above the surface. The stems are simple or slightly branched, 

 and the leaves may be arranged either in whorls or scattered on the 

 stem. The submersed leaves are usually highly dissected and comblike. 



One of the more commonly observed species is the American or 

 northern milfoil, Myriophyllum exalbescens Fern. Stems of this 

 species are simple or forked, with vegetative tissue that has a 

 brownish-purple pigmentation. The deeply dissected leaves develop in 

 whorls of threes or fours (insert 1). The floral spike is the only plant 

 part that emerges above the water surface. Parrot-feather, 

 M. brasiliense Cambess, is a species that is occasionally seen as an 

 escapee from aquarium culture, especially in warmer climates. This 

 species produces emersed leaves that are featherlike and are dissected 

 into 10 or more comblike divisions (insert 2). Flowers of parrot-feather 

 are usually conspicuous as white tufts in the axils of the emersed leaves. 



Flowers on all the species are quite small, having four petals. The 

 fruits are nutlike bodies joined in groups of four. Certain species 

 overwinter by means of winter-buds that develop in the leaf axils. 

 Because of the wide variability of foliage character of plants in this 

 genus, even on the same plant, it is difficult to separate the species. 

 Differences can only be determined by detailed study of flowers and 

 fruits. 



Watermilfoil is a widely distributed aquatic plant that is often 

 found on irrigation systems, particularly in still or slow-moving water. 

 It is considered to be a pest to water distribution systems only in 

 localized situations. 



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