Spiranthes casei Catling & Cruise - Case's Ladies' Tresses


 

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Spiranthes casei - (image 1 of 4)

 

Taxonomy

Family: Orchidaceae

Habitat

Sandy or shaley, acid soil.

Associates

Often with Polytrichum sp.

 Distribution

Nova Scotia (var. novaescotiae); ME to northern PA, west to MI and WI. More northern than S. ochroleuca though the ranges overlap.

Morphology

Perennial to 40 cm. Leaves remaining until anthesis and withering shortly after; flowers 5-7.5 mm, loosely arranged in the inflorescence, evidently in a single spiral; lateral sepals cupped, often falcate; labellum centrally smooth and yellowish; dorsal sepal and petals barely recurved; seeds polyembryonic; 2n=60-62.

Notes

Flowers late August to early September

Wetland indicator: NA

This species is part of the Spiranthes cernua complex. Pace and Cameron (2017) concluded that this species is an ecologically specific subspecies of  S. ochroleuca, however a later study (Hough and Young 2021) found evidence that S. casei is of possible hybrid origin with S. ochroleuca as one of the parent species. Spiranthes casei can be distinguished by its smaller flowers and non-recurved dorsal sepal and petals, and the tendency of the flowers to form a single spiral; it is also a polyploid with polyembryonic seeds, while S. ochroleuca is diploid and produces monoembryonic seeds.

References

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second Ed.
The New York Botanical Garden. Bronx, NY

 

M. Hough and M.A. Young. 2021. A systematic survey of the Spiranthes cernua species complex (Orchidaceae) in New York. Native Orchid Conference Journal, 18(3): 22-56.

 

Pace, M.C. and Cameron, K.M. The systematics of the Spiranthes cernua species complex (Orchidaceae): Untangling the Gordian Knot. Systematic Botany, 42(4):1-30.

 


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 Michael Hough 2017