According to Ceska and Ceska (2010), this species is "Introduced and invasive. North American invasive populations are considered to be of a hybrid origin (M. spicatum x M. sibiricum) by Moody & Les (2002, 2007). Stem drying reddish. No winter buds."

General:
Perennial aquatic from a rhizome, stems usually branched, to 250 cm long, reddish-brown, pinkish-tawny in drying.

Leaves:
In whorls of 3 to 5 mostly 1 cm apart or more on stem, those in the middle whorls usually less than 2.5 cm long, simply pinnate with 12 or more segments on each side of rachis; segments rarely to 1.5 cm long, in a regular, feather-like arrangement, about 1-2.5 mm apart; winter buds absent.

Flowers:
Spikes to about 15 cm long, emergent erect; flowers usually in whorls of 4 in the axils of bracts; all but the lowest bracts essentially entire and shorter than the flowers and fruits, the lowest comb-like to sharply toothed and commonly exceeding the flowers; flowers progressing from basal whorls of pistillate flowers through 1 perfect flower to the upper whorl of male flowers with reddish, soon deciduous petals about 3 mm long; stamens 8.

Fruits:
Mericarps, 4, nearly round, with tiny warts on the dorsal ridges.

Notes:
This species was introduced to British Columbia in the early 1970's and has become a serious aquatic weed. In Hitchcock et al. (1961) plants of this species would key out as "Myriophyllum spicatum var. exalbescens."

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