Let’s talk Spiranthes. This genus of native orchid is entirely successional. They are found exclusively in habitats with an identity crisis; areas neither entirely open prairie nor enclosed by an overhead canopy. Most bloom in the fall, are rarely over a foot tall, have crisp white flowers, and are notoriously the most misidentified native orchid we have.
In Central Illinois, there are 9 species of Spiranthes, Three species are extremely rare or considered extirpated. One species is so fragrant, it can be found with the nose before the eyes. One has a unique green lip, while another is so small, even the trained eye will often overlook. One species in particular, Spiranthes cernua (Nodding Ladies Tresses), appears to be the carbon atom of Spiranthes…it gets around. Spiranthes cernua is a polyploid, appearing to encompass the genome of whatever sister species growing alongside it throughout it’s broad range across the USA. Within Central Illinois, the Spiranthes cernua complex encompasses the now elevated Spiranthes magnicamporum (Great Plains Ladies Tresses) and of course, Spiranthes cernua.
Spiranthes magnicamporum was described from the Spiranthes cernua complex in the 70’s by Charles Sheviak with a plethora of specimen data obtained from the Central Illinois native, Paul Shildneck. S. magnicamporum differs from S. cernua genotypically by being a diploid and only occurring in habitats with calcareous soils. Phenotypically, S. magnicamporum has a noticeable elongated lip with a yellow center and spreading lateral sepals with flowers emitting a potent fragrance. Basal leaves are never present during flowering.
In contrast, Spiranthes cernua is primarily, but not solely found in slightly acid soils. Flowers have a broad lip with pearly undulations, lateral sepals forming a hood, and noticeably nodding flowers with a slight fragrance. Basal leaves occur on most, but not all populations.
These two species are very similar, in addition to one overlapping many key characteristics of the other. To make things more confusing, each population of both lineages appear different even throughout Central Illinois. In some cases, the two are indistinguishable without counting chromosomes.