6. Spiranthes tuberosa Raf. (little ladies’ tresses)

Pl. 117 a, b; Map 486

S. tuberosa var. grayi (Ames) Fernald

S. beckii (Lindl.) House

Flowering stems 15–30(–50) cm long, glabrous. Basal leaves 2 or 3, absent at flowering time, 1–3 cm long, ovate to elliptic, glabrous. Flowers appearing as a single spiral along the flowering stems. Sepals and lateral petals 3.0–4.5 mm long, white, the lateral sepals free to the base or nearly so, only slightly spreading, oriented parallel to the rest of the perianth or nearly so. Lip 2.5–3.5 mm long, oblong, the margins irregularly toothed toward the tip, white without a colored area in the middle of the inner surface. Column 1.5 mm long, green. August–October.

Scattered in Missouri, mostly south of the Missouri River (eastern U.S. west to Texas and Kansas). Dry, upland forests and bluff tops, mostly on acidic substrates; also in old fields and on dry roadsides, often in dry, sterile, cherty or sandy soils; less commonly in lawns.

For a discussion of some of the differences between this species and the related S. lacera, see the treatment of that species. As in S. lacera, variation exists in the density of flowers and tightness of the spiral in the inflorescence. Plants with tighter spirals are sporadic in Missouri and have been called var. grayi (Ames) Fernald. However, there is a lot of intergradation between these taxa and they seem unworthy of formal taxonomic recognition.