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Introduction
According to Ceska and Ceska (2010), Andean watermilfoil is a "South American species that extends to western USA and to British Columbia; also in eastern Canada. It occurs in wind-swept parts of large lakes or in flowing water of rivers. Dried herbarium specimens are dark grey. The lowermost leaves are reduced to bract-like structures and the system of strong whitish roots are the best identification characters of the sterile plants. Winter buds absent."
Species Information
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expanded illustration for this species.
General: Perennial aquatic from a rhizome; stems 20-100 cm long, simple or branched.
Leaves: In whorls of 4 or 5, 1-2.5 cm long, comb-like and dissected into 13-21 threadlike segments, very gradually transitional to the bracts; bracts conspicuous, oblong triangular, 7-10 mm long and from comb-like to lightly sharp-toothed; winter buds absent.
Flowers: Inflorescence simple to conspicuously forked, submersed to emergent; flowers subtended by small, whitish, erose to comb-like bracteoles 1-2 mm long; sepals whitish, more or less sharp-toothed to comb-like; petals soon deciduous, about 2.5 mm long; stamens 8, the anthers about 2 mm long; stigmas feather-like.
There are ten species of Myriophyllum found in the Pacific Northwest (Ceska and Ceska 2010). View a key to the genus Myriophyllum for this region prepared by Oldriska Ceska and Adolf Ceska (BEN #428).
Habitat / Range
Large lakes and rivers in the lowland zone; rare on Vancouver Island; E to PE and S to WA, ID, OR, AZ and MX; S America.
