Ceska and Ceska (2010) say the following about this species: "Circumpolar species. Occurs sporadically throughout Canada, Pacific Northwest, and NE parts of the USA. Stems and leaves green, leaves often with "myriophylloid glands" at the base of the lowermost segments. Winter buds frequent, clavate."

General:
Perennial aquatic from creeping rhizome, wholly submersed, or with the spike and upper leaves sometimes emersed; stems simple or with a few elongate branches up to 250 cm long.

Leaves:
In whorls of 4 or 5; submersed leaves to 45 mm long, with 9 to 13 opposite or alternate pairs of flacid capillary segments to 28 mm long; emersed leaves and bracts smaller and with coarser divisions or merely comb-like pinnate; winter buds well developed at the end of the growing season, 1-4 cm long, club-shaped, broadest at the top.

Flowers:
In whorls of 4-6, perfect or the lower ones female and the upper male; bracteoles minute, palmately 7-lobed, about 0.5 mm long; petals spoon-shaped or rudimentary in female flowers, obtuse, about 2.5 mm long; stamens 8, about 2 mm long.

Fruits:
Mericarps nearly round, 2-2.5 mm long, glabrous or more or less with tiny warts, rounded on back.

Notes:
Mistakenly treated as a synonym of "Myriophyllum spicatum var. spicatum."in Hitchcock et al. (1961).

Source:  The Illustrated Flora of British Columbia

If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Illustration Source:  The Illustrated Flora of British Columbia

Synonyms and Alternate Names:
Myriophyllum scabratum Michx.
Myriophyllum verticillatum var. cheneyi Fassett
Myriophyllum verticillatum var. intermedium W.D.J. Koch
Myriophyllum verticillatum var. pectinatum Wallr.
Myriophyllum verticillatum var. pinnatifidum Wallr.
Potamogeton pinnatum Walter