Distinguishing Yellow Trout Lilies in E USA
It's easy to distinguish our three yellow trout lilies from one another when they are in-fruit, or dug-up. But what about when they're in-bloom? You know, when you notice them?
The presence of stolons can be inferred from the number of one-leaved, 'sterile' plants in a population. The stolon-producing species often produce carpets of plants in this stage; E. umbilicatum subsp. umbilicatum will only produce the occasional cluster of steriles, which are either same-aged siblings (clustered by a single fruit dispersal event) or offsets with the blooming-sized parent eaten/missing.
Clifford Parks and James Hardin (1963) carried out an exhaustive study of their floral characteristics and correlated them to stolon production, ploidy, and capsule shape. I thought the results of their paper might be useful to iNaturalists. They are summarized here:
E. rostratum | E. americanum |
E. umbilicatum subsp. umbilicatum |
E. umbilicatum subsp. monostolum |
tepal carriage | agape | strongly reflexed | strongly reflexed | strongly reflexed |
---|---|---|---|---|
flower angle | erect | nodding | nodding | nodding |
stolons | 1+ | 1+ | 0 | 1 |
capsule shape in profile |
strongly beaked ("rostrate") |
rounded, truncate, or apiculate |
indented ("umbilicate") |
indented rarely merely truncate |
capsule presentation | held erect | not erect but still held off the ground |
reclining on the ground | reclining on the ground or rarely just above |
petal bases | clearly auricled encircling filaments |
minutely auricled or toothed |
not auricled | not auricled, but margin irregular |
green coloration on abaxial side of tepals |
none | none or slight | none | present |
pale spot at base of inside of tepals |
absent | absent in 90% otherwise vague or small |
always present, but sometimes small |
always present often prominent and large |
dark flecking on perianth |
absent | absent or slight | absent or slight, but variable |
always present, few to many |
style thickness just below point of stigmatic divergence |
thickened | thickened | remains thin | remains thin |
stigma lobes | swollen short erect |
swollen long divergent |
slender short divergent |
slender long divergent |
anther & pollen color | yellow always |
yellow or brown-lavender |
brown-lavender rarely yellow |
brown-lavender rarely yellow |
ploidy | diploid | tetraploid | diploid | diploid |
Not included: E. americanum subsp. harperi, because the authors questioned its distinctiveness. It's mainly distinguished from E. americanum subsp. americanum by having (1) more strongly-apiculate capsules and (2) stigma lobes that are 'distinctly grooved distally' and variously described as 'recurved' or merely 'divergent'. It is documented from Alabama, Georgia, Mississippi, and southern Tennessee. Geraldine Allen and Kenneth Robertson consider it to be more reliably distinct and single it out in their treatment of the genus for The Flora of North America entry.