Spiranthes magnicamporum Sheviak

Great plains ladies'-tresses

The specific epithet magnicamporum is the Latin meaning "of the large plain," referring to the prairie habitat that this species is found in.

DESCRIPTION: Plant pubescent above the leaves, 12-38 cm tall (including inflorescence), arising from a cluster of large, fleshy roots, appearing tuberous. Leaves 2-3, basal, oblanceolate to linear-lanceolate, 10-14 cm long and 0.8-1 cm wide, fugacious (withering at flowering), grading into reduced sheathing bracts below the inflorescence, the bracts typically overlapping. Inflorescence a downy, spicate raceme of 20-40 creamy-white to yellowish, fragrant flowers, 12-38 cm tall, dense and multi-ranked, each flower subtended by an elongate, ovate-lanceolate bract. Sepals linear-lanceolate, 6-11 mm long and about 2 mm wide, the lateral sepals with margins inrolled, and typically spreading slightly and ascending with the tips often recurved and nearly meeting above the flower, dorsal sepal connivent with petals to form a hood over the column, sepals creamy-white to yellowish-colored. Petals linear-lanceolate to linear, 7-10 mm long and 1-2 mm wide, closely appressed to the dorsal sepal, tips of dorsal sepal and petals reflexed slightly, colored as sepals. Labellum ovate to obovate and strongly arcuate-recurved, 6.5-11 mm long and 4-6 mm wide, creamy-white to yellowish-colored with the central portion typically thickened and yellowish, the central portion never constricted, the base of the labellum with two small, incurved, pubescent calli.

Easily confused with other species of Spiranthes, particularly S.cernua. The spreading lateral sepals, leafless stem at flowering and odor of S. magnicamporum separate it from most S.cernua, which has appressed lateral sepals, a leafy stem at anthesis and usually scentless flowers. However, there are some races of S.cernuawhich approach many of these aspects of S. magnicamporum. Separating these specimens is extremely difficult, with the best character being embryony: the seeds of S. magnicamporum are monoembryonic, whereas a large percentage of the seeds of S.cernua are polyembryonic. Where the two species co-occur (which is not uncommon in southern Wisconsin), S. magnicamporum typically does not begin blooming until after S.cernua has completed flowering, and occupies drier microsites.

Typically found on dry bluff or hill prairies over limestone or dolomite.

September 5-October 7.

I have seen a bumblebee (Bombus nevadensis ssp. americorum) pollinating Spiranthes magnicamporum in a prairie in southeastern Wisconsin. After visiting a number of inflorescences, the bee began to vigorously scratch at the pollinia on its proboscis, trying to remove them. The bee became so involved in trying to remove the pollinia that it fell to the ground, where it was easily captured. The specimen was determined by Steve Krauth, and is deposited in the Insect Research Collection at the University of Wisconsin-Madison. Apart from this observation, there are no published accounts of pollination of S. magnicamporum.

DISCUSSION: This species was first described by Charles Sheviak in 1973. Until that point, it had masqueraded as a variety of taxa, including Spiranthes odorata (or S. cernua var. odorata) and S. ochroleuca (or S. cernua var. ochroleuca). Fuller (1933) described S. cernua as "very fragrant," probably actually referring to S. magnicamporum, which is strongly fragrant, while S. cernua is weakly fragrant at most. I located a large, dense population of S. magnicamporum in Walworth County by first smelling the flowers, form a distance of about thirty feet. The odor has been described as similar to coumarin. John T. Curtis collected S. magnicamporum (as S. cernua in 1939) and affixed a note to the herbarium sheet that said that the scent was like "Bull Durham tobacco, but sweeter."

Go directly to Wisconsin herbarium records.
Return to the main LIST of the Orchids of Wisconsin.

Return to the main KEY to the Orchids of Wisconsin.