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

Trillium ovatum Pursh
western trillium (Pacific trillium)
(Previously in Liliaceae)

Introduction to Vascular Plants

© David Blevins  Email the photographer   (Photo ID #392)

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Distribution of Trillium ovatum
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Trillium ovatum var. ovatum

Species Information

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Perennial herb from a short, stout, fleshy rhizome; flowering stems erect, 10-45 cm tall, unbranched, smooth throughout.
Stem leaves usually 3 in a whorl, 5-18 cm long, often as wide, broadly egg-diamond-shaped to triangular egg-shaped, smooth, unstalked or nearly so, the margins entire; basal leaves lacking.
Inflorescence a solitary, terminal, stalked flower, the stalk 1-8 cm long; flowers star-shaped, erect to nodding; petals 3, white turning pale pink to purple with age, sometimes pinkish initially, egg-shaped, 3-6 cm long; sepals 3, green and leaf-like, lanceolate to oblong, somewhat shorter than petals; stamens 6; pistil 1, 3-chambered.
Capsules, berry-like, green to yellowish, broadly egg-shaped, with wing-like ridges; seeds numerous, large, egg-shaped, in a sticky mass when first shed.
Two varieties occur in BC:

1. Plants 20-45 cm tall; flowers opening white; the common variety........................ var. ovatum

1. Plants 10-20 cm tall; flowers opening pink; rare on western Vancouver Island..................... var. hibbersonii (Taylor & Szczawinski) Douglas & Pojar

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist forests in the lowland, steppe and montane zones (var. ovatum), and mossy bluff ledges and river boulders in the lowland zone (var. hibbersonii); common in S BC, south of 50degreeN; E to SW AB and S to CO and CA.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Trillium ovatum

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 5 670 1816
Slope Gradient (%) 0 18 95
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
0 315 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 4 7
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: CDF(139), CWH(467), ESSF(82), ICH(197), IDF(20), MH(1), MS(33), PP(2)

Ecological Indicator Information

A shade-tolerant/intolerant, submontane to montane, Western North American forb distributed more in the Pacific than the Cordilleran region. Occurs in maritime to submaritime cool mesothermal climates on fresh to very moist, nitrogen-rich soils; its occurrence decreases with increasing elevation, latitude, and continentality. Scattered on water-receiving sites; usually associated with Achlys triphylla, Galium triflorum, Polystichum munitum, Streptopus amplexifolius, and Tiarella trifoliata. A nitrophytic species characteristic of Moder and Mull humus forms.

SourceIndicator Plants of Coastal British Columbia (Information applies to coastal locations only)


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 cool mesothermal.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References