Trillium decumbens
Trillium parviflorum
decumbent trillium, trailing wakerobin
small-flower trillium
short, thick.
horizontal to ± erect, brownish, thick, praemorse, not brittle.
1–2, decumbent, usually by an S-shaped curvature, round in cross section, 0.5–2 dm, somewhat stout, slightly expanded toward bracts, densely puberulent, especially just below bracts and on bases of main bract veins beneath.
1–3, round in cross section, 1.7–3 dm, slender to robust, glabrous.
appearing early in season, in good condition for only a few weeks after anthesis, dying back to semipersistent bases early, resting on ground surface, sessile;
blade strongly mottled in shades of green and bronze and with silvery overlay, mottling becoming obscure with age, ovate to suborbicular, 4–12 × 3.3–7 cm, apex acute to rounded.
held well above ground, sessile;
blade green with widely scattered mottling, mottling becoming obscure with age, ovate to broadly ovate, 6.5–16 × 5–8 cm, not glossy, apex obtuse.
erect, odor unreported;
sepals divergent, green- or maroon-streaked, lanceolate-ovate, 22–48 × 9–14 mm, margins entire, flat, apex acute;
petals long-lasting, rigidly erect, ± connivent, ± concealing stamens and ovary, dark maroon-purple when fresh, fading especially distally to dull reddish brown, greenish brown, or with creamy yellow tones, very rarely pale lemon yellow forms occur, twisted (but not spiraled), linear-lanceolate or oblanceolate, 4–8+ × 0.7–1 cm, thick-textured, margins entire, apex acute;
stamens erect, straight, dark purple, 10–25 mm;
filaments dark purple, 2–5 mm;
anthers straight, dark purple, 9–20 mm, dehiscence extrorse;
connectives broad, extending to 3.5–4 mm beyond anther sacs;
ovary dark purple, oval, 6-angled, 5–10 mm;
stigmas erect, divergent-recurved, distinct, sessile, pink or white, subulate, 4.5–8 mm.
erect, odor spicy, of cloves;
sepals displayed above bracts, spreading, divergent, green, lanceolate, 16–25 × 4–8 mm, margins entire, flat, apex variously obtuse to rounded;
petals long-lasting, erect to erect-spreading, ± connivent, ± concealing stamens and ovary, white, occasionally purple stained basally, sometimes weakly spirally twisted, linear to linear-lanceolate, 2.2–4.5 × 0.4–1 cm, thin-textured, base occasionally cuneate, margins entire, apex obtuse;
stamens erect, 10–15.5 mm;
filaments white, greenish white, or purple stained, 1–3 mm, much shorter than anthers, slender;
anthers erect, straight, greenish white, 9–11+ mm, ± slender, dehiscence latrorse;
connective greenish, straight, barely extended (to 0.4 mm) beyond anther sacs;
ovary green or green and purple basally, ovoid, obscurely 6-gonal, 4–8 mm;
stigmas erect, ± divergent, distinct, green, outer surface purple, subulate, 3–4.5 mm, ± fleshy, thickened.
baccate, dark purple, broadly ovoid to subglobose, crownlike, strongly ridged, 1–1.5 × 1 cm, pulpy but not juicy, present and enlarging on naked scapes until early autumn.
dark reddish purple or maroon, fragrance not reported, subglobose, ± 1 cm, ± juicy.
= 10.
= 10.
Trillium decumbens
Trillium parviflorum
Trillium decumbens occurs in the Ridge and Valley and Cumberland Plateau physiographic provinces. It has a large, deep, horizontal rhizome, the growing point of which always faces downslope.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Trillium parviflorum varies from very short, slender, small-bracted plants to tall, broad, umbrella-bracted giants. Regardless of plant or bract sizes, flower and petal sizes are remarkably constant, all plants having small, linear-lanceolate petals. This is not usually the case with T. albidum, the species with which this plant is most likely to be confused. In T. albidum also the plants can be enormous, but when they are, the petals are very long, broad, and conspicuously obovate-diamond-shaped. In large clonal clumps of T. albidum, the larger and more mature offsets show the typical petal shape, while the smaller and presumably youngest offsets sometimes produce smaller, narrower petals, more like those of T. parviflorum.
Some western botanists, more experienced with local populations than I, do not consider Trillium parviflorum to be distinct from T. albidum. They point out that since there is an extensive region of apparent intergradation (as indeed there is, well supported by herbarium vouchers), there exists a morphological cline from the long- and wide-petaled T. albidum to the narrower- and generally shorter-petaled T. parviflorum, and that T. parviflorum, therefore, should not be considered a separate species but rather a subspecies or a variety. Since no one to date has treated T. parviflorum at the subspecific or varietal level, and since in my own limited experience it does appear as a distinct species in Washington north of the Columbia River, I include it here as treated by Soukup. I have seen populations of considerable variation north of Corvallis, Oregon, and agree that there is much overlap with T. albidum. Obviously there is need for a much more extensive study of this situation.
A factor that exacerbates this problem (and many others in Trillium), is that nutrition, age, and even favorable position in the habitat can greatly influence plant and floral organ sizes. In many species, including T. albidum, when a single vigorous clonal clump produces many offsets, the oldest offsets may have flowers with very large petals, sepals, ovary, etc., while the younger offsets may have organs only half the size. In most sessile trilliums particularly, population averages are often more useful than isolated individual measurements, a difficult situation, indeed.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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