Trillium underwoodii
Trillium pusillum
longbract wakerobin, Underwood's trillium
dwarf trillium, dwarf wakerobin, least trillium, little trillium
horizontal, brownish, short, thick, praemorse, not brittle.
horizontal, branching, thin.
1–2, round in cross section, 0.8-2 dm, slender to stout, glabrous.
1–2, round in cross section, 0.7–2 dm, slender, becoming taller and more robust after flowering, glabrous.
usually drooping, often touching ground in early anthesis, sessile;
blade pale silvery green, strongly mottled in 3 or more shades of dark green and bronze, sometimes maroon, mottling becoming obscure with age, ovate-lanceolate to obovate, 6.5–12 × 5–7.8 cm, margins of distal 1/3 straight from rounded base to apex, apex acuminate.
very short-petiolate, subsessile or sessile;
blade dark green with maroon undertones when young, not mottled, 3–5 major veins from base, oblong to lanceolate-obtuse, 2.5–8+ × 1–3 cm, not glossy, apex obtuse.
erect, odor fetid, especially when first open;
sepals displayed above bracts, spreading, green or purple on adaxial surface, lanceolate, 4.5–5 × 8–12 mm, margins entire, flat, apex rounded-acute;
petals long-lasting, erect-spreading, ± connivent, ± concealing stamens and ovary or at least partially obscuring stamens, tips ± incurved, dark maroon-red, or purplish red, brownish maroon, or yellowish green, not spirally twisted, oblanceolate to elliptic, 3–5.5+ × 1–1.5 cm, usually 3–4 times longer than wide, thick-textured, margins entire, apex acute;
stamens ± erect to weakly incurved, 14–17 mm;
filaments purple, 1–2 mm;
anthers 8–15 mm, thick, dehiscence latrorse;
connectives brown-purple, straight, extended 1–2 mm beyond anther sacs, apex somewhat acute;
ovary purple, ellipsoid, 6-angled, 6.3–11 mm;
stigmas erect, abruptly recurved upon ovary, distinct, purplish, linear, 1.5–5 mm, slightly thickened basally, fleshy.
above bracts, erect, odorless to faintly sweet, pedicellate or sessile;
sepals conspicuous, spreading to same plane as petals, dark green with maroon undertones when young, oblong-lanceolate, 15–30 × 5–10 mm, margins entire, apex obtuse to strongly rounded;
petals of short duration, spreading-ascending, exposing stamens and ovary, weakly recurved in distal 1/2, white, aging to deep rosy pink abaxially, veins not engraved but major petal veins clearly visible, oblong to narrowly lanceolate, 1.5–3 × 0.5–1.5 cm, thin-textured, widest above base, margins strongly undulate, quite variable in petal width and degree of undulation between individuals and populations, apex obtuse to weakly acute;
stamens erect-spreading, 8–10 mm;
filaments pinkish purple to white, ± equaling or slightly shorter than anthers, slender;
anthers ± straight, pale lavender or yellow, 3–8(–10) mm, thicker than filaments, dehiscence introrse;
connectives not extended beyond anther sacs;
ovary conspicuous, white, ovoid, obscurely 6-angled, 2.5–8 mm, attachment narrower than ovary;
stigmas confluent with style, greenish white to white, distally 3-lobed, lobes linear (threadlike), long-spreading, 3–12 mm, uniformly thin and threadlike;
pedicel stiffly erect to leaning, 0.5–2 cm, or absent to much reduced.
baccate, purple-black to dull greenish maroon, odorless, ovoid to obovoid, 6-angled (-ridged), 0.7–1 cm diam., pulpy, not juicy.
white or pale greenish, ovate, 1–1.5 cm, pulpy, moist but not juicy.
= 10.
Trillium underwoodii
Trillium pusillum
Trillium underwoodii can cause considerable confusion for the beginning student of the genus. In some ways it closely resembles a small-statured T. cuneatum. As T. underwoodii continues to expand after flowering, it may become somewhat taller and less “ground hugging,” and it then appears similar to a smaller plant of T. decipiens, which grows in parts of the same range, especially when its bracts do not touch the ground at anthesis. It also has vague similarities to T. reliquum, with which it grows sympatrically in parts of its range. Care should be taken to observe the details of floral structure accurately.
Distribution of Trillium underwoodii is much more restricted than that given by J. K. Small (1933), who indicated a range extending from Alabama to North Carolina and Arkansas.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
Trillium pusillum comprises widely disjunct, regional populations, each varying somewhat from the others and variable within itself as well. Some of these populations have been named as varieties or separate species. In the wild, the plants that have been recognized as var. ozarkanum generally grow taller than others and are said to have bracts with five major veins instead of three. Plants attributed to var. texanum, on the other hand, are generally smaller in all parts, with narrower petals, and often revert to a single bract when not flowering. Only var. virginianum is easily distinguished at sight by its “sessile” flower. This variety has received extensive study. P. R. Cabe (1995), in a morphological study including statistical analysis, found variation within and between populations. He felt that his results were inconclusive, and also that some of the variation might be environmentally induced. The variation that he found did not correlate with a geographic pattern, and he suggested treating all Virginia populations as var. virginianum, or simply T. pusillum. In a later study, P. R. Cabe and C. R. Werth (1995), using isozyme evidence, obtained like results, and suggested treating all Virginia populations as a single variety pending further investigation. Until there has been such study, of the Virginia plants as well as the rest of the T. pusillum complex, I choose to retain the fairly distinctive and more or less traditionally known var. virginianum, and include all other populations in a broadly circumscribed var. pusillum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Flower pedicillate; pedicel usually 0.5–2 cm. | var. pusillum |
1. Flower sessile or subsessile; pedicel, if present, 0.1–0.3 cm | var. virginianum |
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