Orchid family (Orchidaceae)
Description: This perennial plant is usually 4-12" tall and unbranched. There is a rosette of 2-6 strap-like basal leaves that are individually about 3-8" long and 1/3" (8 mm.) across. They are linear to linear-oblanceolate with smooth margins, and usually wither away before the flowers bloom. On robust specimens, there may be 1 or 2 small leaves on the lower flowering stalk. The flowering stalk is up to 1' tall, with 6-12 flowers occurring on the upper half. These flowers are arranged on the stalk as intertwined double spirals – as a result, the individual spirals are not readily discernible. The flowering stalk is light green and covered more or less with white glandular hairs. At the base of each flower, there is a conspicuous green bract that is curved and narrowly ovate. Each flower is about 1/3" (8 mm.) long, consisting of 3 white sepals and 3 white petals. The upper sepal and upper two petals are fused together and form a curved hood that curls upward at its tip, forming a small upper lip with 3 lobes. The lower petal has a prominent lip that hangs downward and has a crystalline appearance, while the lateral sepals are linear and non-spreading. Together, these sepals and petals form a tubular-shaped flower that nods downward. The blooming period can occur from late summer until the fall, and lasts about a month. There is usually a mild floral scent. Some plants may form cleistogamous flowers. Fertilized flowers are replaced by pods containing the tiny seeds, which are easily carried aloft by the wind. These pods may be capable of photosynthesis while they are green. The root system consists of a cluster of fleshy roots at the base of the plant that are finger-like in shape, and occasional rhizomes may be produced. This orchid can reproduce from the seeds of the flowers, or it may form offsets from rhizomes. Normal growth and development won't occur unless the root system forms an endomycorrhizal association with the appropriate species of fungus.
Cultivation: For most ecotypes of this orchid, the preference is full or partial sun and moist sandy soil. Some ecotypes appear to flourish in thin rocky soil that is rather dry. Taller, more aggressive plants can out-compete this orchid for the available light, so it prefers rather open ground vegetation. Starting plants from seed is quite difficult; on the other hand, this orchid is easier to transplant than most others. Cultivars of this orchid species are available from the mass horticultural market, while local ecotypes are next to impossible to obtain.
Range & Habitat: Nodding Ladies' Tresses occurs occasionally throughout Illinois, where it is native; for an orchid species, it is fairly common (see Distribution Map). Habitats include moist sand prairies, sandy savannas, areas adjacent to paths in sandy woodlands, shrubby bogs, sandy pannes near lakes, gravelly seeps, limestone glades, bluffs, sandy pits, ditches, and abandoned fields. This orchid typically occurs in somewhat disturbed areas of high quality habitats, and appears to respond positively to occasional wildfires. Individual plants are usually scattered about, rather than forming dense colonies.
Faunal Associations: Both long-tongued and short-tongued bees occasionally visit the flowers for nectar. The seeds are too small to be of any interest to birds. The foliage can be eaten by various mammalian herbivores, including rabbits, groundhogs, and deer, while the fleshy roots are probably eaten by pocket gophers when individual plants stray into drier areas.
Photographic Location: The photographed plant was growing in a sandy swale at the Indiana Dunes National Lakeshore in NW Indiana.
Comments: While rather small-sized, the bright white spike of flowers provides a striking contrast with the background vegetation and is fairly easy to spot. The individual flowers are attractive, particularly when they are viewed close-up; in particular, the lower lip has an intricate crystalline pattern that can vary significantly from flower to flower. Unlike the Ladies' Tresses orchids that form a single spiral of flowers, such as Spiranthes lacera (Slender Ladies' Tresses), the Nodding Ladies' Tresses falls into the group of Spiranthes spp. with double intertwined spirals that are difficult to discern because of the density of flowers on the spike. The Spiranthes spp. in this group are distinguished from each other primarily by considering the variation in the structure of their flowers and the shape of their leaves. Nodding Ladies' Tresses can be distinguished from these other species by the downward curve of its tubular flowers, providing them with a 'nodding' appearance.