E-Flora BC: Electronic Atlas of the Flora of British Columbia

Elatine rubella Rydb.
three-flowered waterwort (southwestern waterwort)
Elatinaceae (Waterwort family)

Introduction to Vascular Plants
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Distribution of Elatine rubella
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Southwestern starwort is a tiny short-lived perennial aquatic or semi-aquatic species found primarily in North America in the western half of of the United States and one Canadian province (British Columbia) (USDA 2011). In British Columbia, it is found in wet ditches, mudflats and shallow ponds and shorelines in the lowland, steppe and montane zones, where it is rare in extreme SW and SC BC (Douglas et al. 1999).

Lomer (2011) describes this species in the Fraser Valley: "A small prostrate annual of wet muddy sites, often half buried. It grows in the wettest depression pools on tidal mudflats and flood pools along the Fraser, Pitt and Harrison Rivers. 14 sites are known in Greater Vancouver, all along the riverflats, except for one site on the shore of Latimer Lake in Surrey, where it is very scarce and was not found in recent years. It will rarely show up from time to time in Fraser River sand dredgings used as preload in preparation for building construction (UBC: Lomer 97-604)." (Reprinted from Botanical Electronic News # 435, with permission)

Species Information

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Annual or short-lived perennial, aquatic or semi-aquatic herb; stems prostrate to erect, 3-10 cm long.
Opposite, simple, oblong-lanceolate, short-stalked, tips blunt to notched, 0.8-1.2 cm long.
Inflorescence of 1 or 2 axillary flowers per node; petals reddish, 3, widely elliptic; sepals usually 2; stamens 3, opposite the sepals.
Capsules, 3-chambered; seeds narrowly oblong, straight or slightly curved, pitted in longitudinal rows.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Wet ditches, mudflats and shallow ponds and shorelines in the lowland, steppe and montane zones; rare in extreme SW and SC BC; E to NB and S to MO, VA, TX, NM, CO and CA.

Source: The Illustrated Flora of British Columbia


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Elatine triandra Schkuhr

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References