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sessile trillium, sessile-flower wake-robin, toad trillium, toadshade

Idaho trillium, long-petioled trillium, petioled wakerobin, purple trillium, purple wakerobin, round-leaf trillium

Rhizomes

horizontal, brownish, thick, praemorse, fleshy.

± erect, often very deep, praemorse.

Scapes

1–3, round in cross section, 0.8–2.5 dm, slender to stout, glabrous.

typically 1, vertical but mostly subterranean, round in cross section, 0.4–1.7 dm, robust, glabrous.

Bracts

held well above ground, sessile;

blade green to bluish green, strongly to sparsely mottled, mottling becoming obscure with age, oval to suborbicular, 4–10 × 2–8 cm, base broadly attached, apex rounded-acuminate to bluntly parallel sided-acuminate (rounded basally to its broad attachment).

just at or slightly above soil, long-petiolate;

blade medium green, not mottled, ovate to elliptic, 7–14 × 5.5–10.2 cm, not glossy, apex obtuse or rounded;

petiole arising from scape apex at or near ground surface, 5–12 cm;

bract and petiole strongly resembling leaves of Plantago.

Flower

erect, odor pungent, spicy;

sepals displayed above bracts, spreading, green, variously streaked with maroon, lanceolate-oblanceolate, 9–35 × 4–8 mm, margins entire, apex rounded-acuminate;

petals long-lasting, erect, ± connivent, ± concealing stamens and ovary, maroon, brownish maroon, green, or yellowish green, not spirally twisted, oblanceolate to elliptic, occasionally almost orbicular, 1.7–3.5 × 0.7–2 cm, thick-textured, narrowed near basal attachment (but not truly clawed), margins entire, apex gradually rounded-tapered to acute;

stamens straight, 10–23 mm;

filaments red-purple, 2–5 mm, dilated basally;

anthers erect, straight, gray-purple, 9–16 mm, thick, dehiscence introrse;

connectives purplish brown, straight, projecting 2–5+ mm beyond anther sacs;

ovary greenish white basally, purple distally, ovoid to globose, 6-angled, pyramidally narrowed to stigmas, 4–8.5 mm;

stigmas erect, divergent-recurved, distinct, purple, subulate, 1–5 mm, ± fleshy.

in axil of bracts at or near ground level, ± erect, odor unknown;

sepals erect to widely spreading, often weakly recurved near middle, green, oblong-elliptic to oblanceolate, 22–47 × 7–10 mm, margins entire, apex acute;

petals long-lasting, ± connivent, ± concealing stamens and ovary, or erect-spreading early then ± connivent, erect to incurved, light maroon-red, purple, or greenish to yellowish, not spirally twisted, flat, linear-lanceolate, 3–5.5 × 0.4–1 cm, thick-textured, margins entire, apex acute;

stamens erect, (15–) 22–30 mm;

filaments olive, (3–)5–7 mm, slender;

anthers straight, brown or olive, 16–20 mm, slender, dehiscence latrose;

connectives yellow or orange, ± not extending beyond anther sacs;

ovary white, greenish, purplish distally, ovoid, sharply angled, 4–9 mm;

stigmas erect, divergent, distinct, purple or olive, linear-subulate, 7–20 mm, apex somewhat recurved.

Fruits

baccate, dark greenish purple, odorless, subglobose, 6-angled, angles somewhat winglike, pulpy, not juicy.

fragrance not reported, ovoid, strongly angled/winged, ca. 1 cm, pulpy, moist.

2n

= 10.

= 10.

Trillium sessile

Trillium petiolatum

Phenology Flowering spring (Mar–early May). Flowering spring (early Apr–late May).
Habitat Rich woodlands, limestone districts, calcareous soils, floodplains, riverbanks, clayey alluvium, less fertile soils, high, dry limestone woods, persists under light pasturing, in fencerows and brushy areas after lumbering Lower rocky hillsides just above stream flats, under brush, edges of coniferous and deciduous forests, open grassy glades, river-flats, wet, seasonally swampy ground and edges of sloughs
Elevation 100–300 m (300–1000 ft) 400–1400 m (1300–4600 ft)
Distribution
from FNA
AL; AR; IL; IN; KS; KY; MD; MI; MO; NC; NY; OH; OK; PA; TN; VA; WV
[WildflowerSearch map]
[BONAP county map]
from FNA
ID; OR; WA
[WildflowerSearch map]
[BONAP county map]
Discussion

Trillium sessile is rather uniform throughout its range, with few color forms.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 26, p. 115. FNA vol. 26, p. 113.
Parent taxa Liliaceae > Trillium > subg. Phyllantherum Liliaceae > Trillium > subg. Phyllantherum
Sibling taxa
T. albidum, T. angustipetalum, T. catesbaei, T. cernuum, T. chloropetalum, T. cuneatum, T. decipiens, T. decumbens, T. discolor, T. erectum, T. flexipes, T. foetidissimum, T. gracile, T. grandiflorum, T. kurabayashii, T. lancifolium, T. ludovicianum, T. luteum, T. maculatum, T. nivale, T. ovatum, T. parviflorum, T. persistens, T. petiolatum, T. pusillum, T. recurvatum, T. reliquum, T. rivale, T. rugelii, T. simile, T. stamineum, T. sulcatum, T. underwoodii, T. undulatum, T. vaseyi, T. viride, T. viridescens
T. albidum, T. angustipetalum, T. catesbaei, T. cernuum, T. chloropetalum, T. cuneatum, T. decipiens, T. decumbens, T. discolor, T. erectum, T. flexipes, T. foetidissimum, T. gracile, T. grandiflorum, T. kurabayashii, T. lancifolium, T. ludovicianum, T. luteum, T. maculatum, T. nivale, T. ovatum, T. parviflorum, T. persistens, T. pusillum, T. recurvatum, T. reliquum, T. rivale, T. rugelii, T. sessile, T. simile, T. stamineum, T. sulcatum, T. underwoodii, T. undulatum, T. vaseyi, T. viride, T. viridescens
Name authority Linnaeus: Sp. Pl. 1: 340. (1753) Pursh: Fl. Amer. Sept. 1: 244. (1814)
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