Trillium ovatum
Trillium parviflorum
Pacific trillium, trillium, western trillium, western wake-robin, western white trillium, white or western trillium, white trillium
small-flower trillium
semierect to horizontal, short, stout, praemorse.
horizontal to ± erect, brownish, thick, praemorse, not brittle.
1–2, round, 2–5 dm, ± slender, glabrous.
1–3, round in cross section, 1.7–3 dm, slender to robust, glabrous.
sessile, subsessile, or short-petiolate;
blade medium green, sometimes blotched and mottled, main veins prominent, ovate-rhombic, 7–12 × 5–20 cm, continuing to expand during anthesis, base rounded, apex acuminate.
held well above ground, sessile;
blade green with widely scattered mottling, mottling becoming obscure with age, ovate to broadly ovate, 6.5–16 × 5–8 cm, not glossy, apex obtuse.
erect or nodding, odorless;
sepals spreading to horizontal, green, lanceolate to oblong-lanceolate, 15–50 × 6–20 mm, margins entire, apex acute;
petals erect-ascending, usually wide-spreading from base, exposing entire pistil, white or with pink or blush markings, lacking V-shaped markings, fading to rosy pink, purple, or dark red, veins not deeply engraved, ± linear to widely obovate, 1.5–7 ×1–4 cm, widest at or above middle, thin-textured, margins flat to undulate, apex acuminate;
stamens prominent, slightly recurved-spreading to straight, 10–18 mm;
filaments white, shorter than anthers, slender;
anthers yellow, 4–16 mm, slender, dehiscence latrorse-introrse;
ovary green or white, ovoid, 6-angled, 5–12 mm, attachment ± 3/4 ovary width;
stigmas recurved, barely connate basally, greenish white or white, linear, not lobed adaxially, 6–10 mm, uniformly thin;
pedicel erect to leaning, 2–6 cm.
erect, odor spicy, of cloves;
sepals displayed above bracts, spreading, divergent, green, lanceolate, 16–25 × 4–8 mm, margins entire, flat, apex variously obtuse to rounded;
petals long-lasting, erect to erect-spreading, ± connivent, ± concealing stamens and ovary, white, occasionally purple stained basally, sometimes weakly spirally twisted, linear to linear-lanceolate, 2.2–4.5 × 0.4–1 cm, thin-textured, base occasionally cuneate, margins entire, apex obtuse;
stamens erect, 10–15.5 mm;
filaments white, greenish white, or purple stained, 1–3 mm, much shorter than anthers, slender;
anthers erect, straight, greenish white, 9–11+ mm, ± slender, dehiscence latrorse;
connective greenish, straight, barely extended (to 0.4 mm) beyond anther sacs;
ovary green or green and purple basally, ovoid, obscurely 6-gonal, 4–8 mm;
stigmas erect, ± divergent, distinct, green, outer surface purple, subulate, 3–4.5 mm, ± fleshy, thickened.
baccate, green or white, ± odorless, broadly ovoid, obscurely winged, 1.2–2.8 × 0.7–1.9 cm, pulpy-moist.
dark reddish purple or maroon, fragrance not reported, subglobose, ± 1 cm, ± juicy.
= 10.
= 10.
Trillium ovatum
Trillium parviflorum
Varieties 2 (2 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Trillium parviflorum varies from very short, slender, small-bracted plants to tall, broad, umbrella-bracted giants. Regardless of plant or bract sizes, flower and petal sizes are remarkably constant, all plants having small, linear-lanceolate petals. This is not usually the case with T. albidum, the species with which this plant is most likely to be confused. In T. albidum also the plants can be enormous, but when they are, the petals are very long, broad, and conspicuously obovate-diamond-shaped. In large clonal clumps of T. albidum, the larger and more mature offsets show the typical petal shape, while the smaller and presumably youngest offsets sometimes produce smaller, narrower petals, more like those of T. parviflorum.
Some western botanists, more experienced with local populations than I, do not consider Trillium parviflorum to be distinct from T. albidum. They point out that since there is an extensive region of apparent intergradation (as indeed there is, well supported by herbarium vouchers), there exists a morphological cline from the long- and wide-petaled T. albidum to the narrower- and generally shorter-petaled T. parviflorum, and that T. parviflorum, therefore, should not be considered a separate species but rather a subspecies or a variety. Since no one to date has treated T. parviflorum at the subspecific or varietal level, and since in my own limited experience it does appear as a distinct species in Washington north of the Columbia River, I include it here as treated by Soukup. I have seen populations of considerable variation north of Corvallis, Oregon, and agree that there is much overlap with T. albidum. Obviously there is need for a much more extensive study of this situation.
A factor that exacerbates this problem (and many others in Trillium), is that nutrition, age, and even favorable position in the habitat can greatly influence plant and floral organ sizes. In many species, including T. albidum, when a single vigorous clonal clump produces many offsets, the oldest offsets may have flowers with very large petals, sepals, ovary, etc., while the younger offsets may have organs only half the size. In most sessile trilliums particularly, population averages are often more useful than isolated individual measurements, a difficult situation, indeed.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Bracts sessile; petals lanceolate to obovate, 1.5–7 × 1–4 cm | var. ovatum |
1. Bracts distinctly short-petiolate; petals linear to linear-lanceolate, 0.5–2.4 × 0.2–0.6 cm | var. oettingeri |
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
