Nuttall's waterweed is a perennial aquatic species that is found in North America across much of the United States and in five Canadian provinces (BC, MB, ON, NB, QC) (USDA 2011). In British Columbia, it is found in "lakes, ponds and streams in the lowland, steppe and montane zones" in the southern part of the province (Douglas et al. 1999). Lomer (2011) provides the following discussion of the species in the Fraser Valley: "An aquatic plant mostly of shallow water along the major rivers. It looks like the common Elodea canadensis, but the leaves are narrower and toothed along the upper margins and the male flowers are sessile and break free from the leaf axils and float to the surface for pollination. Known from 12 sites in Greater Vancouver, all along the Fraser and Pitt Rivers (UBC: Lomer 97-584). It is to be expected in other sites up the valley and will likely be removed from the rare plant list eventually because it is widespread in BC and often overlooked. It can survive in polluted water and has been introduced to places far outside its native range." [Originally reprinted from Botanical Electronic News #435, with permission]

General:
Perennial aquatic herb from a fibrous root; flowering stems several, branched at the nodes.

Leaves:
Stem leaves in whorls of 3, linear to linear-lanceolate, narrowly tapering to the pointed tips, 6-13 mm long, 0.3-1.8 mm wide, minutely sharp-toothed.

Flowers:
Inflorescence of either male or female, axillary, solitary flowers, the male flowers unstalked, breaking away and floating to the surface where they open; petals 3, white, elliptic, 0.5-1 mm long or lacking (male) or 2-3 mm long (female); sepals 3, greenish, broadly lanceolate, about 2 mm long (male) or 2-3 mm long (female); stamens 9.

Fruits:
Capsules, cylindric or egg-shaped, 5-7 mm long; seeds several, short soft-hairy, about 4 mm long.

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:
Anacharis nuttallii Planch.
Anacharis occidentalis (Pursh) Victorin
Elodea columbiana H. St. John
Elodea minor (Engelm. ex Caspary) Farw.
Elodea occidentalis (Pursh) H. St. John
Philotria angustifolia (Muhl.) Britt. ex Rydb.
Philotria minor (Engelm. ex Caspary) Small
Philotria nuttallii (Planch.) Rydb.
Philotria occidentalis (Pursh) House
Udora verticillata var. minor Engelm. ex Caspary