Trillium erectum L., Sp. Pl. 1: 340. 1753.

Type:— USA. Habitat in Virginia, s.d., s.coll (LINN!, lectotype designated by Reveal, Phytologia 72: 1–4, 1992) .

Heterotypic synonyms:

Trillium pendulum Willd., Neue Schriften Ges. Naturf. Freunde Berlin iii, 421. 1801. Type not located.

Trillium rhomboideum var. atropurpureum Michx,. Fl. Bor. Amer. 1: 215. 1803. Invalid name.

Trillium rhomboideum Michx., Fl. Bor. Amer. 1: 215–216. 1803. nom. superfl., cited T. erectum L. as synonym.

Trillium foetidum Salisb., Parad. Lond. Tt. 35. 1805. Type:— USA. Virginia: Bartram s.n. Type not located.

Trillium acuminatum Raf., Med. Repos. 5: 361. 1808. Type not located.

Trillium album Small, in part, see T. rugelii .

Trillium erectum var. album (Michx.) Pursh, Fl. Amer. Sept. (Pursh) 1: 245. 1814. Type:— North America. Sep., Michaux s.n. (holotype: P 00730404 digital image).

Note:— This name is based on Michaux’s T. rhomboideum var. album . Pursh (1814) based his new combination on Michaux’s name, but this appears to have been without observation of Michaux’s type gathering because it (at P) is evidently T. rugelii (see below), whereas the K specimen of T. erectum var. album Pursh is a white-flowered form of T. erectum .

Trillium erectum var. atropurpureum Pursh, Fl. Amer. Sept. 1: 245. 1814 [1813]. Type:— USA. Amer., Sept., Michaux s.n. (holotype: not located; isotype: P00730489 digital image!).

Trillium purpureum Kin ex Elliott (1817: 430) . A sketch of the botany of South-Carolina and Georgia 1: 430. Type:—USA. Pennsylvania: Philadelphia, Kin s.n. (holotype: PH digital image!; isotype: MO 2140261!) .

Trillium latifolium Raf., Med. Fl. 2: 96. 1830. Type:—In Kentucky. Type not located.

Trillium nutans Raf., Med. Fl. 2: 99. 1830. Type:—From Canada to Carolina. Type not located.

Trillium flavum Raf., Med. Fl. 2: 100. 1830. Type:—In the mountains from New York to Virginia. Type not located.

Trillium spatulatum Raf., Med. Fl. 2: 101. 1830. Type:—In the mountains Alleghany. Type not located.

Trillium divaricatum Raf., Med. Fl. 2: 102. 1830. Type:—In the Alleghany and Cumberland mountains . Type not located.

Trillium atropurpureum M.A.Curtis ex L.C.Beck, Bot. North. Middle States 361. 1833. Type not located.

Trillium rhombifolium Raf., Autik. Bot 133. 1840. Type:—Apalachian [sic] Mts. Alabama & c. Type not located.

Trillium erectum var. flavum Torr., Fl. New York 2: 296. 1847. Type:— USA. New York: Hamilton or Madison counties, Douglas s.n. (holotype: NY 00319877 digital image!; isotypes: GH 00030156 digital image!), non, Trillium erectum var. flavum H.H.Eaton ex A.Eaton, nom. nud.

Trillium erectum subsp. rubrum Clute, Amer. Bot. (Binghamton) 9: 76. 1905. nom. nud.

Note:— Clute (1905) discussed the default name for the type color form, reddish, and the necessity, if it was at all worthy of formal description, to name the color forms that are different from the typical color form and often co-occur with one or more color forms.

Trillium erectum f. albiflorum, Ralph Hoffm. Proc. Boston Soc. Nat. Hist. 36: 244. 1922. Type:— USA. Massachusetts: Berkshire County, Stockbridge, rich woods, 23 May 1920, Hoffman s.n. (holotype: NEBC 00032163!).

Trillium erectum var. cahnae Farw., Amer. Midl. Naturalist 9: 266. 1925. Type:— USA. Michigan: Oakland, Vicinity of Clawson, 12 May 1924, Cahn 6874a (holotype: BLH0000369 digital image!).

Trillium erectum f. sessiloides Boivin, Rhodora 55: 102. 1953. Type:— CANADA. Ontario: Carleton, Beechwood, close to the cemetery gate, May 1899, s.coll. 1822 (holotype: DAO000466292 digital image!).

Trillium erectum L. var. horizontale Louis-Marie, Rev. Oka Agron. Inst. Agric. 14: 151. 1940. Type:— CANADA. Quebec: Comté des Deux-Montagnes, bois riche, N.- E. à Ontario, 30 Apr 1958, Meunier s.n. (holotype: S-G-7309 digital image!) .

Notes:— Within populations of T. erectum and its close relative T. sulcatum, plants can exhibit an array of floral color variation and orientation. Variation is often found regionally where the characters are consistent, but there are regions also where great variability within a single population has been observed. For instance, in the southern Appalachians, flowers can be white, greenish, yellow, pink, and typical maroon. The typical predominant color form is maroon, but in the Southern Appalachians white forms exist in large uniform colonies (see also T. simile). In most populations, a single color is predominant with only occasional other colors, whereas other populations can have a mixture. The position of the flower can also vary from the typical form with erect peduncles and the flowers held facing outward, but some populations have the peduncles held horizontally in plane with the leaves, declining below the plane of the leaves, or pendent like those of T. rugelii or T. vaseyi . This variation we consider to be normal and do not recognize formal designations based on color or flower position in most cases. An exception, if found to be genetically distinct, are the large white flowered plants forming uniform populations in some regions of the Southern Appalachians (see also under T. simile).