Target Species: Great Plains Ladies’ Tresses (Spiranthes magnicamporum).
Fingers of prairie penetrate central and eastern Texas like roots in the form of the Blackland Prairies and pockets of grasslands in the Pineywoods, Post Oak Savannah, and Edward’s Plateau. In scattered areas within these prairies, where the soil conditions are just right, the fall air is filled with the sweet fragrance of the Great Plains Ladies’ Tresses (Spiranthes magnicamporum). From mid October through November, spirals of delicate white flowers push their way through a sea of prairie grasses and deliver their aroma to the wind.
Commonly referred to as ladies’ tresses, the genus Spiranthes is named in reference to the spiral arrangement of flowers along the inflorescence. Spiranthes orchids are a confusing group to identify, particularly those of the Spiranthes cernua complex, to which the Great Plains Ladies’ Tresses belongs. There are, however, several ways to differentiate S. magnicamporum from the much more common and widespread S. cernua, which I will outline below.
The first, most readily observable difference is in the habitat. Spiranthes cernua is fairly catholic in its preference, occurring in a variety of disturbed habitats including moist roadside ditches, utility right-of-ways, fallow fields, and even residential lawns. Spiranthes magnicamporum, however, occurs under much more specific conditions. In Texas they generally occur in prairies with soils that are both alkaline (basic) and calcareous (composed of calcium carbonate). They can tolerate dryer conditions, and can be found on exposed outcrops of limestone and sandstone.
Another difference is in the fragrance. While S. cernua has little to no odor, S. magnicamporum is intensely fragrant. It gives off a rich scent of coumarin which can sometimes be detected before the plant is seen. In fact, as I photographed some of these orchids from several feet away I enjoyed the pleasant aroma filling the air.
There are some that will say that a careful examination of the seeds is required to differentiate S. cernua and S. magnicamporum. There are, however, several morphological aspects of the plant and its flowers that are often used to identify S. magnicamporum in the field. In general, S. magnicamporum appears more robust, with a thicker stem and slightly larger flowers. The lateral sepals of S. magnicamporum are generally spreading, and arch above the rest of the flower, especially as the blooms age. In S. cernua, the sepals are adpressed, held tightly against the rest of the flower. The lip of S. magnicamporum is also slightly elongated and thickened. The lip of S. magnicamporum also displays a faint yellow wash, in contrast with the typically pure white lip of S. cernua. See the photo of Spiranthes cernua below for comparison.
Carolina and I first looked for Spiranthes magnicamporum in a number of Weches Outcrops in East Texas. Having no luck there, the next day we traveled to a series of sandstone outcrops in the Blackland Prairie in East-Central Texas. Here we found them to be quite common, but only in areas where the underlying sandstone approached the surface. It was quite a treat to see them growing directly on exposed sandstone alongside a variety of cacti and yucca. The Great Plains Ladies’ Tresses are frost hardy, with reports of blooming as late (early?) as January. Indeed, the night before we set out had dipped into the low 30s, yet the flowers remained fresh and fragrant. Searching for these lovely orchids among the prairie with my wife was the perfect way to spend a brisk fall day. As we headed back to the dense forests of the Pineywoods we marveled at prairie skyscape, painted pink and orange by the setting sun.