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Key to Trillium

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Show caption*© Alan Cressler: Trillium cuneatum, Chattahoochee National Forest, Towns County, Georgia 3 by Alan Cressler
1 Leaves mottled with 2-3 different shades of green and silver (very rarely the mottling not apparent); flower sessile; [subgenus Sessilia]
1 Leaves solid green; flower on a pedicel (the pedicel sometimes very short or essentially absent in some varieties of T. pusillum).
image of plant
Show caption*© Alan Cressler: Trillium erectum (color complex), Stony Bald, Blue Ridge Parkway, Buncombe County, North Carolina 2 by Alan Cressler
  2 Petals relatively thick in texture, straight-margined, maroon or white, rarely yellow or green (if white, turning brown with age); stigmas thicker at base, tapering gradually toward tip, distinct; ovary purple-black, maroon, pink, or white, 6-angled; [subgenus Trillium]
image of plant
Show caption*© Richard & Teresa Ware
  2 Petals relatively delicate in texture, wavy-margined, white to deep pink (if white, generally fading to pink with age); stigmas thin, uniform in thickness from base to apex, somewhat fused at the base into a short style; ovary greenish-white to white, 3- or 6-angled or-lobed

Key to Trillium, Key A: trilliums with sessile flowers and mottled leaves (subgenus Sessilia)

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1 Plants prostrate, with scapes very short, holding bracts (leaves) near the ground; floral fragrance of rotting meat or manure-scented
  2 Anther dehiscence extrorse; bract apices rounded or obtuse, typically mottled only in 2 colors, silver and green
  2 Anther dehiscence introrse; bract apices obtuse or acute, conspicuously mottled in silver and three or more shades of green
    3 Rhizome 0.3-1 cm in diameter, branching, forming clonal patches; scape straight, ascending, densely puberulent on angles; bract blades typically < 6 cm long; petals 1.5-3 cm in length, widest at middle; floral fragrance of horse manure
    3 Rhizome 0.8-1.5 cm in diameter, unbranched, not forming clonal patches; scape S-shaped, decumbent or semi-decumbent, glabrous; bract blades typically > 7 cm long; petals (2.2-) 3.0-5.0 (-6.0) cm in length, widest above the middle; floral fragrance of rotten meat
1 Plants erect or ascending, with tall scapes holding bracts (leaves) well above ground, or sometimes bract tips barely touching the ground in early anthesis; floral fragrance various, foetid, pleasant, or mildly unpleasant
      4 Sepals abruptly deflexed between and below the leaves, distinctly descending below the approximately horizontal plane of the leaves; filaments about as long as incurved anthers; [T. recurvatum group].
        5 Anther connectives slightly incurved or erect; filaments short (< ½ the anther length); [variously endemic to either Kershaw and Richland counties in the inner Coastal Plain of SC (Trillium oostingii) or Hamblen and Hawkins counties in the Ridge and Valley of TN (Trillium tennesseense)].
          6 Ovary 6-16 mm long; filaments less than ½ as long as the ovary; stigma lobes ca. 1× as long as the ovary, the stigmatic surfaces smooth; [endemic to Kershaw and Richland counties in the inner Coastal Plain of SC]
          6 Ovary 2-4 mm long; filaments about equal to the ovary; stigma lobes ca. 2× as long as the ovary, the stigmatic surfaces strongly crested-undulate; [endemic to Hamblen and Hawkins counties in the Ridge and Valley of TN]
        5 Anther connectives strongly incurved; filaments long, > ½ the anther length; [primarily west of the Blue Ridge and south into the Gulf Coastal Plain, very rarely disjunct to the Mountains or upper Piedmont].
             7 Leaves sessile or subsessile, borne in a descending or drooping manner (similar to the sepals); petals usually 4-7× as long as wide, strongly clawed
             7 Leaves distinctly petiolate, borne in an ascending manner (strongly contrasting in position with the strongly deflexed sepals); petals usually ca. 2× as long as wide, attenuate to weakly clawed
      4 Sepals erect, ascending, or spreading, usually borne at or above the approximately horizontal plane of the leaves; filaments much shorter than the upright anthers.
               8 Petals spreading to horizontal, with 1-2 spiral twists (looking something like an airplane propeller); anther dehiscence extrorse (toward the outside of the flower); [T. sessile group]
               8 Petals erect to slightly spreading, not spirally twisted; anther dehiscence introrse (toward the inside of the flower), or latrorse (toward the side).
                 9 Petals broadly spatulate, clawed, broadly rounded (though sometimes with an apiculus) at the tip; petals pale lemon-yellow (the claws greenish or maroon); flower fragrance clove-like; [of the Savannah River drainage, from sw. NC southeastward along the GA-SC border]; [T. sessile group]
                 9 Petals lanceolate, elliptic, obovate, or oblanceolate, but not broadly spatulate and distinctly clawed, generally acute at the tip; petals maroon-red, purplish-brown, yellow, or green; flower fragrance various; [collectively widespread in our area].
                   10 Stigmas > 1.5× as long as the ovary; stamens about 0.5× as long as the petals; anther connectives prominently prolonged into a beak 1.0-5.0 mm long (beyond the anther sacs); [T. sessile group]
                   10 Stigmas as long as the ovary or shorter; stamens < 0.5× as long as the petals; anthers blunt, the connectives extended < 1.0 mm beyond the anther sacs.
                     11 Ovary ellipsoid; leaves acute, the margins of the outer 1/3 more or less straight; leaf blade mottled with 3 or more shades of green, the palest shade forming a very conspicuous pale silvery-green streak along the midvein; [of the Coastal Plain and fall-line area of GA, AL, and FL Panhandle]; [T. sessile group].
                       12 Stem 2.5-3× as long as the leaves; petals oblanceolate-obovate, usually 1.5-3× as long as wide; flower fragrance yeasty-sweet (or similar to overripe bananas)
                       12 Stem 1-2× as long as the leaves (though sometimes elongating late in the season); petals narrowly elliptic to oblanceolate-obovate, usually 3-5× as long as wide; flower fragrance yeasty-sweet (or reminiscent of stale beer)
                     11 Ovary ovoid; leaves acute to acuminate, the margins of the outer 1/3 convex; leaf blade mottled with 2-3 shades of green, paler shades sometimes prominent along the midvein, but not as above; [collectively widespread in our area]; [T. maculatum group].
                          13 Petals < 4× as long as wide, elliptic-oblanceolate to oblanceolate; [of inland provinces, rarely in the Coastal Plain].
                            14 Flower fragrance fruity-spicy, like green apples or Calycanthus (rarely musky); petals maroon, bronze, green, yellow; portions of ovary and stamens purplish during anthesis
                            14 Flower fragrance lemon-like; petals greenish-yellow darkening to yellow; ovary and stamens greenish-white during anthesis
                          13 Petals > 4.5× as long as wide, narrowly oblanceolate-spatulate to linear-oblanceolate; [of the Coastal Plain, rarely farther inland].
                                16 Leaf apices blunt to rounded; leaf upper surface with numerous stomates across the surface (visible as white dots with 10× magnification); stamens ca. 1.5× as long as the ovary
                                16 Leaf apices acute; leaf upper surface lacking stomates (or present only near apex); stamens ca. 2× as long as the ovary
                                  17 Ovary 3-angled at base of stigmas (rarely 6-angled); petals 7-17 mm wide, narrowly spatulate (appearing clawed); outer whorl of stamens broader, anther dehiscence introrse; flower fragrance faintly spicy-fragrant, banana-like; [of AL, n. FL, GA, and e. SC]
                                  17 Ovary 6-angled; petals 3-8 mm wide, linear-oblanceolate, narrowly elliptic, to linear-lanceolate (weakly or not clawed); flower fragrance putrid, like rotting meat; [of MS, LA, and e. TX].
                                    18 Stamens <1.5× as tall as the ovary; [of c. and e. LA and w. MS].

Key to Trillium, Key B: trilliums with unmottled leaves and pedicellate flowers, of subgenus Trillium

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1 Flowers held below the leaves (the pedicel declined below a horizontal plane).
  2 Stamens far exceeding the pistil, filaments as long as the ovary or longer, at least partly maroon, the anther sacs yellow to maroon; ovary small, globose, 3-12 mm long, dark purplish black; flower fragrance pungent, rose-like; pedicel long, 3-13 cm long; petals strongly overlapping, usually maroon (rarely white or whitish)
  2 Stamens at most 1.5× longer than the pistil, filaments shorter than the ovary, white (less commonly purplish), the anther sacs lavender to vivid purple (or albino); ovary white to pink or dull red, large, ovoid, 10-17 mm long; flower fragrance various; pedicel short to long, 1.5-12 cm long; petals not strongly overlapping, usually white (rarely maroon).
    3 Pedicels short, 1.5-4 cm long.
      4 Anthers 7.5 mm long or less, about as long as the filaments or shorter; petals narrowly elliptic to obovate, often scarcely larger than the sepals, delicate, occasionally margined in pink or green; [of damp forests of n. VA and northward]
      4 Anthers 7.0 mm long or more, longer than the filaments; petals ovate to elliptic, much broader than the sepals; [of mesic forests of n. NC southward]
    3 Pedicels long, 4-12 cm long.
        5 Stamens about as long as the ovary or slightly longer; filaments short, ca. 1/3 the length of the anthers or shorter; filaments ½ as long as the ovary or shorter; pollen creamy to pale yellow; filaments and anthers white, the anthers at least in part somewhat appressed against the ovary
        5 Stamens far exceeding ovary height; filaments ca. ½ the length of the anthers; pollen creamy, yellow, or pale grayish purple; anthers and filaments also variable in color, mostly white, occasionally purplish; anthers mostly longer than the ovary and not appressed against it
1 Flowers held at or above the level of the leaves (the pedicel nearly horizontal, inclined above the horizontal, or erect).
          6 Ovary flask-shaped, broadest near the base, usually white to pinkish (sometimes darker); petals usually white to creamy white (maroon forma occasional).
             7 Stamens about as long as the ovary or slightly longer; filaments short, ca. 1/3 the length of the anthers or shorter; filaments ½ as long as the ovary or shorter; pollen creamy to pale yellow; filaments and anthers white, the anthers at least in part somewhat appressed against the ovary
             7 Stamens far exceeding ovary height; filaments ca. ½ the length of the anthers; pollen creamy, yellow, or pale grayish purple; anthers and filaments also variable in color, mostly white, occasionally purplish; anthers mostly longer than the ovary and not appressed against it
          6 Ovary globose, widest near the middle, black to purplish black; petals white, maroon, yellowish, or otherwise.
               8 Petals lanceolate to narrowly ovate or elliptic, spreading from base in the same plane as the sepals, rarely > 2× as broad as the sepals; sepals 0.5-0.8× as long as the pedicel, weakly sulcate-tipped (roundly keeled and upturned near apex); flower fragrance unpleasant, musty.
               8 Petals ovate, overlapping in some instances and forming a cup-shaped base, variably recurved apically, > 2× as broad as the sepals; sepals 0.2-0.7× as long as the pedicel, sulcate-tipped; fragrance pleasant, sweet to fungal.
                 9 Sepals 0.4-0.7× as long as the pedicel; leaves broadly elliptic; stamens 1.2-1.8× pistil height; flowers generally large, petals much longer than the sepals; sepals green; petals usually white (rarely maroon); flower fragrance sweet, like green apples
                 9 Sepals 0.2-0.4× as long as the pedicel; leaves broadly obovate; stamens 0.9-1.6× pistil height; flowers relatively small, petals only slightly longer than the sepals; sepals suffused with purple; petals usually maroon (rarely white); flower fragrance fungal, like fresh mushrooms

Key to Trillium, Key C: trilliums with unmottled leaves and pedicellate flowers, of subgenus Delostylis and subgenus Callipetalon

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1 Petals white with triangular red blaze (rarely entirely white or pinkish); anther sacs lavender to white, dehiscence extrorse; fruit a red berry; leaves long-acuminate; [of acidic sites in the Mountains, generally strongly associated with either Pinus, Tsuga, Picea, Rhododendron, or other heaths]; [genus Trillidium]
1 Petals white to deep pink, lacking a red blaze; anther sacs yellow, dehiscence introrse; fruit a white to greenish-white, fleshy, irregularly dehiscent capsule; leaves obtuse to acute (or somewhat acuminate in T. grandiflorum); [of less distinctly acidic sites, collectively widespread in our area].
  2 Pedicel declined below the leaves (rarely erect); sepals arcuate-recurved; anthers irregularly twisted outward; pollen egg-yolk yellow; [subgenus Delostylis]
  2 Pedicel inclined above leaves to strictly erect; sepals not arcuate-recurved; anthers erect, regular; pollen light yellow (richer yellow in T. grandiflorum).
    3 Sepals narrower than the petals, acute; anthers white to greenish-white between the anther sacs; leaves obtuse, acute, or acuminate; pedicel somewhat angled from the vertical.
      4 Ovary obscurely 3-lobed; leaves < 5 cm long, blue-green, obtuse; [subgenus Callipetalon]
      4 Ovary sharply 6-angled (-winged); leaves > 5 cm long, green, acute to acuminate.
        5 Petals obovate, tightly rolled at base, abruptly flared near the apex; leaves broadly elliptic, acuminate; style minute, < 1.0 mm long; [subgenus Callipetalon]
        5 Petals elliptic, loose, gradually separating; leaves ovate, acute; style conspicuous, > 1.5 mm long; [subgenus Delostylis]
    3 Sepals about as broad as the petals or broader, obtuse; leaves obtuse; anthers purplish-green between anther sacs; pedicel erect through fruiting; [Trillium pusillum complex of subgenus Delostylis].
          6 Leaves with stomates on the upper surface, appearing farinose; [of n. GA]
             7 Leaves linear, > 4× as long as wide; [of n. GA]
             7 Leaves ovate or elliptic, not linear, < 4× as long as wide; [of sw. AR, nw. LA and e. TX]
          6 Leaves without stomates on the upper surface, appearing glabrous.
               8 Pedicels < 10 (-12) mm long.
                 9 Pedicels (0-) 0.5-1.0 mm long; leaves (1.5-) 2.0-2.4 (-2.9)× as long as broad; leaves (14-) 15-20 (-22.5) mm wide; filaments (4.5-) 4.6-5.8 (-8) mm long; [of upland forests of Mountains of w. VA and e. WV]
                 9 Pedicels (0.5-) 1.0-6.6 (-11) mm long; leaves (2.1-) 2.5-3.8 (-6)× as long as broad; leaves (6-) 10-17 (-25) mm wide; filaments (2.5-) 3-5 (-6.5) mm long; [of wetland forests].
                   10 Anthers (3.2-) 4.5-6 (-7) mm long; stamens (5.7-) 8.4-10.9 (-12.5) mm long; stigmas (1-) 2.1-3 (-5) mm long; leaves elliptic; [of the outer Coastal Plain of e. MD, e. VA, and ne. NC]
                   10 Anthers (2.5-) 2.7-4.8 (-6.8) mm long; stamens (5.7-) 6-9.2 (-13.2) mm long; stigmas (1-) 1.2-2.5 (-4.7) mm long; leaves ovate; [of the upper Coastal Plain and Piedmont of ne. NC, se. VA, and Mountains of sw. VA].
                     11 Pedicels (0.5-) 1-2.1 (-7) mm long; stamens (6-) 7.5-9.2 (-11) mm long; stigmas (1-) 2-2.5 (-4.7) mm long; [of upper Coastal Plain of e.VA]
                     11 Pedicels (1.2-) 1.8-6.6 (-11) mm long; stamens (5.7-) 6-7.6 (-13.2) mm long; stigmas (1-) 1.2-2 (-2.5) mm long; [of Piedmont to edge of upper Coastal Plain of ne. NC]
               8 Pedicels 10-56 mm long.
                       12 Leaves ascending; sepals ca. 1.4× as long as the petals; [of sphagnum bogs in the s. SC sandhills]
                       12 Leaves horizontal to declining; sepals 0.9-1.1× as long as the petals.
                          13 Leaves narrower, (1.9-) 3-4.1 (-5.6)× as long as wide; pedicels (23-) 25-33 (-56) mm long; [of calcareous savannas and swamps]
                          13 Leaves broader, (2-) 2.7-3.4 (-5.5)× as long as wide; pedicels (7-) 13-30 (-45) mm long.
                            14 Leaves ovate, acute; sepals (14-) 22-30 (-41) long, (4-) 6-11 (-17) mm wide, (2-) 3-4.3 (-5.6)× as long as wide; [generally of upland rocky slopes]
                            14 Leaves elliptic, rounded; sepals (13-) 18-25 (-30) long, (4-) 6-8 (-12) mm wide, (1.8-) 2.7-3.1 (-4)× as long as wide; [generally of swamps and floodplains]
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