Trillium kurabayashii is a species of flowering plant in the bunchflower family Melanthiaceae. The species is endemic to the western United States, occurring in extreme southwestern Oregon, northwestern California, and the Sierra Nevada of northern California. It was first described by John Daniel Freeman in 1975. The specific epithet kurabayashii honors Masataka Kurabayashi, a Japanese cytologist and population geneticist who first postulated the taxon’s existence. It is commonly known as the giant purple wakerobin, a reference to its conspicuously large, dark purple-red flower, one of the largest of any sessile-flowered trillium. Unlike most other authorities, the influential Jepson Manual does not recognize Trillium kurabayashii as a distinct species. This discrepancy has led to widespread confusion regarding the identification and distribution of other purple-flowered trilliums native to California, namely Trillium angustipetalum and Trillium chloropetalum. Description Trillium kurabayashii is a perennial herbaceous plant that persists by means of an underground rhizome. Like all trilliums, it has a whorl of three bracts (leaves) and a single trimerous flower with 3 sepals, 3 petals, two whorls of 3 stamens each, and 3 carpels fused into a single ovary with 3 stigmas. Since its flower has no stalk, T. kurabayashii belongs to subgenus Sessilium, the sessile-flowered trilliums. Scape erect, long, usually 2.3–2.5 times as long as the bracts. Bracts sessile, ovate or widely ovate, long, dark green, with tips generally slightly acuminate. Sepals lanceolate, long, diverging, greenish or basally purple. Petals oblanceolate, long, usually 3.3–4.6 times longer than wide, erect, dark purple (variously referred to as maroon-red, red-purple, purple-red, or lurid purple), underside usually duller than the top. Stamens erect, long; filaments short, dark purple; anther sacs introrse, long, with yellow pollen; connectives prolonged up to 0.5 mm. Carpels approximately 4/5 as tall or equal to the stamens; ovary ovoid, tall, dark purple, a rounded hexagon in cross section; stigmas coarsely subulate, long, erect, dark purple. Flowers have a spicy or musty odor at anthesis, sometimes becoming fetid with age. Fruit dark reddish purple, ovoid to ellipsoid, weakly angled, , fleshy. Trillium kurabayashii has one of the largest flowers of any sessile-flowered trillium. Petals up to long have been recorded. Similar species Trillium kurabayashii is often confused with other sessile-flowered trilliums in the western United States, partially due to morphological similarities but also because of long-standing disagreements regarding taxonomy. The following key was published by Freeman in 1975: The ranges of Trillium kurabayashii and T.