Spiranthes cernua (L.) Rich.

Common Ladies' Tresses

© SRTurner

Family - Orchidaceae

Habit - Perennial forb, lacking rhizomes.

Stems - Flowering stems erect, single and unbranched, 10-50 cm long, with sparse to dense, glandular hairs.

Leaves - Mostly basal, 3-4, often absent at flowering time, 5-23 cm long, linear to linear-oblong, glabrous. Cauline leaves reduced to scales, these to 3 cm long, sheathing, acuminate, entire, glabrous.

Inflorescence - Terminal helical spike to 12 cm long. Flowers appearing as though in 2 or more ranks or intertwined spirals along the flowering stems or sometimes no spirals discernable. Flowers sessile, subtended and partially enveloped by a single acuminate bract. Bracts to 1.2 cm long, 5 mm broad (at the base), pubescent, with broad scarious margins in the basal 1/2, the apices abruptly acuminate.

	Inflorescence.
© DETenaglia

Flowers - Sepals and lateral petals 6-11 mm long, white to light cream colored, the lateral sepals free to the base or nearly so, oriented parallel to the rest of the perianth and only slightly spreading. Lip 8-11 mm long, ovate to oblong, sometimes somewhat constricted in the middle, the margins entire or somewhat irregular toward the tip, white to light cream colored, often tinged with yellow or greenish yellow in the middle of the inner surface. Column 4 mm long, green.

	Flowers.
© SRTurner

Furits - Capsules, elliptic, ascending, 4-10 mm long, with longitudinal ribs.

Flowering - August - November.

Habitat - Acidic glades, upland prairies, wet meadows, thickets, old fields on acidic substrates.

Origin - Native to the U.S.

Lookalikes - Other species of Spiranthes, especially S. magnicamporum.

Other info. - This is one of the more common orchids in Missouri, occurring more or less throughout the state, but less common in the northern regions. It is found throughout the eastern half of the continental U.S. Identification of Spiranthes is easy due to their corkscrew inflorescences of small, urn-shaped white flowers. However, identification to species can be challenging, and in fact this species was not differentiated from S. magnicamporum until 1973. S. cernua is characterized by a glandular inflorescence, relatively large flowers, and lateral sepals which are more or less aligned with the main perianth and not spreading outward much. The throat of the perianth is not green.

The species name cernua means "nodding," and the flowers do indeed nod slightly. The colloquial term "ladies' tresses" refers to the fancied resemblance of the inflorescence to a woman's braided hair.

Photographs taken in Tuftonboro, NH., 10/2000 (DETenaglia); also at Crowley's Ridge Conservation Area, Stoddard County, MO, 7-17-2009, and in Fremont, Newaygo County, MI, 9-11-2016 (SRTurner).