Trillium simile Gleason, Bull. Torrey Bot.

Floden, Aaron J. & Knapp, Wesley M., 2023, Typification of the North American species of Trillium subg. Trillium (Melanthiaceae: Parideae), Phytotaxa 599 (3), pp. 193-200 : 197

Trillium simile Gleason, Bull. Torrey Bot. Club 33: 391. 1906.

Type:— USA. North Carolina: moist woodlands near Tryon, 28 April 1904, Gleason 14933-a (holotype: NY00051079 digital image!) .

Homotypic synonyms: Trillium vaseyi var. simile (Gleason) Barksdale, J. Elisah Mitchell Sci. Soc. 54: 285. 1938. Trillium erectum var. vaseyi f. simile (Gleason) Ahles, J. Elisah Mitchell Sci. Soc. 80: 172. 1964.

Notes:— The concept of T. simile has been greatly expanded and the morphological characters misapplied since its description. Gleason (1906) compared T. simile to T. rugelii in his description and diagnosis of this new species, stating it differed by its longer stamens, yellow anthers (vs. purple), and proportionately longer filaments. Gleason was familiar with T. rugelii and its typical habit of declining to reflexed flowers held beneath the leaves, so his comparison of this novelty suggests that the type gathering of T. simile had flowers held beneath the leaves. In his description, he even stated that the peduncles were “declined or cernuous” ( Gleason 1906). Barksdale (1938) placed T. simile at varietal status under T. vaseyi , also confirming the original concept of Gleason (1906) that the flowers were pendent. Barksdale (1938) was confident that T. simile was merely a color variant of T. vaseyi occurring in mixed populations with the white form being rare but also in isolated uniformly white-flowered populations. Peattie (1927) argued that T. simile has erect peduncles, but sometimes declined flowers based on the type gathering and his field experience. Although the type at NY does have the flowers in an upright position, it is not apparent whether this is due to a pressing artifact or the plants truly having erect peduncles. The current concept is that of a large plant, with erect peduncles, large creamy-white petals that usually are overlapping at their bases, a dark ovary, and yellow pollen ( Case & Case 1997, Case 1997). Forms like this occur throughout the Southern Appalachians ( Case 1997). Some specimens have been observed in herbaria that share this morphology from Ohio, West Virginia, and Virginia (AF pers. obs.). Barksdale (1938) said that Small’s (1933) treatment could apply to nearly any white-flowered erect Trillium with a dark ovary, and it appears that the current concept does not match the type based on the protologue in which Gleason (1906) compared his new species to T. rugelii .

Floral fragrance in Trillium has been used as a field character when comparing related species. Peattie (1927), Small (1933), Case (1997), and others have mentioned the sweet or delicious floral scent of T. simile , which the authors have observed on various erect and reflexed forms in the Southern Appalachians that fit both concepts of T. simile . A form that is common in and around the Great Smoky Mountain National Park (North Carolina and Tennessee) at lower elevations on rich mesic slopes has been considered the typical form with large creamy-white, erect flowers ( Case & Case 1997), but this form has a fragrance identical to that of the higher elevation reddish forms of T. erectum , i.e., wet dog or egg whites. Forms with erect peduncles have been observed with a sweet applelike fragrance, and declining forms observed in western North Carolina and northern Georgia have been observed with a distinctive spicy clove-like or a tea rose-like fragrance. Like T. flexipes , it may be that the fragrance changes temporally over the flowering period to attract potential pollinators or to even deter herbivory, and that the volatiles producing the fragrance vary during the day due to temperature. In addition to the fragrance difference, T. simile differs from T. erectum in its much longer filaments and anthers that surpass the ovaries, but there has never been a wide-range study that surveys this character and its taxonomic value. Molecular analyses of T. subg. Trillium may resolve this complex of white-flowered species.