Giant Trillium, Great Trillium, Sessile Trillium: Trillium albidum ssp. albidum (Synonym: Trillium chloropetalum) - Scapes usually 2.2–5.8 dm; petals white to creamy white, rarely very pale pink or pinkish basally, oblanceolate to obovate in outline, 4.8–8 cm long.
Small-flowered Trillium, Small-flowered Wakerobin: Trillium albidum ssp. parviflorum (Synonyms: Trillium chloropetalum, Trillium parviflorum) - Scapes usually 1.7–3 dm; petals white, rarely purplish basally, linear to linear-lanceolate in outline, 2.2–4.5 cm long.
Giant Purple Wakerobin: Trillium kurabayashii (Synonym: Trillium angustipetalum) - Scape 2.5–5.5 dm; petals glossy dark maroon-red or purple, oblanceolate in outline, spreading-erect, 5.5–11 × 2–3.5 cm, margins ± flat, widest at or below middle, wedge-shaped basally; stigmas 6–8 mm; n California and extreme sw Oregon.
Western Wake-robin, Wakerobin, Trillium, Pacific Trillium: Trillium ovatum ssp. ovatum - Petals white, often with pink or blush markings, aging to deep rosy pink, purple, or dark red, erect-ascending, widely spreading in distal half, distal margins usually flat to weakly undulate to undulate, scarcely touching basally to overlapping and forming tube, not concealing ovary when viewed from above, linear to obovate in outline, 1.5–7 long × 1–4 cm wide; w North America.
Brook Trillium, Brook Wakerobin: Trillium rivale (Synonym: Pseudotrillium rivale) - Sepals shorter and narrower than petals, apex rounded-apiculate; petals white, usually sparsely to very heavily flecked with madder-purple, color not changing with age, erect-spreading, ovate-cordate to ± orbicular, widest at or beyond middle, round-tapered distal to middle to apiculate-acuminate tip, margins mostly without undulations; Siskiyou Mountains of n California and Oregon.