Trillium gracile, and T. ludovicianum may both be present in eastern Texas. These are my notes for distinguishing them from one another, taken from the monograph where John Freeman first described T. gracile and clarified the previously-hazy description of T. ludovicianum. Where metrics are given, I have omitted the extreme values, providing only the "typical" ranges (not in parentheses). Other Trillium also occur in Texas. By "leaves" I mean, technically, "bracts".
T. gracile | T. ludovicianum | |
---|---|---|
scape | ||
scape length : leaf length | 3.2 - 3.5 | 2.4 - 2.8 |
leaf | ||
shape | elliptic (elliptic-ovate to elliptic-oblong) |
lanceolate or broadly ovate |
sepal | ||
length | 18 - 26 mm | 24 - 40 mm |
apex shape | acuminate-blunt or obtuse | acute or acute-rounded |
petal | ||
length | 21 - 35 mm | 35 - 55 mm |
stamen | ||
anther sac dehiscence |
introrse | latrorse |
pollen color | creamy - yellow | olive - orange |
anther connective prolongation |
short-beaked | short-rounded |
gynoecium | ||
carpel-height : stamen-length | barely exceeding 0.5 | ≥ 0.75 |
ovary x-section | 3-angled | 6-angled |
stigma length | 2.0 - 4.5 mm | 4.5 - 10 mm |
stigma attachment | divergent extending ovary outline into lyre-shape |
initially continuous in outline with ovary bending distal to point of attachment |
fruit | ||
outline | smooth | often prominently 6-ridged |
I have seen comments suggesting that clump-formation and overall plant size differ between the two species, with T. ludovicianum being both more likely to form clumps and generally taller. These are not mentioned in Freeman's monograph. He gives an overlapping range of scape lengths for the two species, with T. gracile being actually taller on average (though it has petals that are about 2 cm shorter):
Trillium gracile: (16-) 20-32.5 (-36) cm long scapes
Trillium ludovicianum: (10-) 15-28 (-37) cm long scapes
Singlehurst et al. (2003) summarized the occurrences of Trillium in Texas. Changes from Freeman's monograph germane to their separation by morphology:
The two species are probably at least partially temporally isolated with T. gracile blooming later: late Mar -May vs. late Feb - early Apr.
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