Contains 5 accepted taxa overall.

Characteristics
Myriophyllum L.
WATERMILFOIL
Classification
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SAXIFRAGALES
Myriophyllum
Citation
MYRIOPHYLLUM Linnaeus, Sp. Pl. 992. 1753.
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TYPE: Myriophyllum spicatum Linnaeus Lectotypified by Britton & A. Brown, Ill. Fl. N. U.S., ed. 2. 2: 614. 1913.
Species
Scientific Name Common Name Herbarium Specimens Status Photos
Myriophyllum aquaticum Parrot-feather
Myriophyllum heterophyllum Southern Water-milfoil
Myriophyllum laxum Loose Water-milfoil
Myriophyllum pinnatum Alternate-leaved Water-milfoil
Myriophyllum spicatum Eurasian Water-milfoil
Identification Key
1.  Plants dioecious (only pistillate in North America); leafy stems mostly emersed; petiole 5-7 mm long; all leaves pectinate; emersed leaves mostly 2.5-3.5 cm long
1.  Plants monoecious, lower flowers pistillate, upper staminate; leafy stems mostly submersed; petiole <2 mm long; submersed leaves pectinate; emersed leaves pinnately divided, serrate, or bract-like, <2 cm long
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2.  Leaves gray-green to dark green, strictly whorled, typically retaining their shape upon drying; stamens 8
2.  Leaves green to reddish green, pseudowhorled to alternate (may appear whorled), typically collapsing and entangled upon drying; stamens 4
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3.  Leaf division typically 12-28 per leaf; distal flowers whorled; fruit prominently beaked
3.  Leaf divisions typically 8-16 per leaf; distal flowers alternate; fruit short-beaked
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4.  Bracts 1-3 mm long, shorter than most inflorescence internodes, pectinate to entire; fruit surface smooth to papillose
4.  Bracts 4-10 mm long, subequal to longer than inflorescence internodes, pinnatifid to pectinate; fruit surface tuberculate
Genus Synonyms
Synonym Full Citation Basionym Type
No synonyms found.