Small whorled pogonia orchid

Arethusa medeoloides Pursh, Fl. Amer. Sept. 2: 591. 1814; Pogonia affinis Austin ex A. Gray

Herbs, singly or rarely in small clumps, short-rhizomatous, 4–25 cm. Stems pale grayish green, glaucous; scales 2–4, near soil line, white to light green. Leaves pale grayish green; blade elliptic-obovate, 17–85 × 8–40 mm, apex acuminate, glaucous when young. Flowers subsessile, without nectar and fragrance; sepals arching, green to light green, linear-oblanceolate, 12–25 × 2–3 mm; petals light green, oblanceolate, 12–18 × 2–4 mm; lip light yellowish green to pale greenish white, streaked with green, obovate, 11–16 × 4–5 mm, lateral lobes narrowly triangular, margins involute, middle lobe rounded, margins slightly revolute, undulate; callus yellowish green, longitudinal, becoming elongate, with fleshy, wartlike papillae toward apex; column 8–10 mm; ovary 10–15 mm; rostellar flap reduced. Capsules 12–28 × 2–10 mm; pedicel of mature capsule elongating to 5–17(–20, rarely) mm. 2n = 18.

Flowering May--Jun; capsules mature fall. Acidic soils, in dry to mesic 2d-growth, deciduous or deciduous-coniferous forests; typically light to moderate leaf litter, open herb layer (occasionally in dense ferns), moderate to light shrub layer, relatively open canopy; frequently on flats or slope bases near canopy breaks; of conservation concern; 30--1000 m; Ont.; Conn., Del., Ga., Ill., Maine, Md., Mass., Mich., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va.

Isotria medeoloides should be sought in Alabama, Arkansas, Indiana, Kentucky, and West Virginia. Isotria medeoloides is self-pollinating (L. A. Mehrhoff 1983). Nonflowering plants commonly have a white, arrested floral bud (1–2 mm).

SELECTED REFERENCES

Brumback, W. E. and C. W. Fyler. 1988. Monitoring of Isotria medeoloides in New Hampshire. Wild Fl. Notes 3: 32–40. Dyer, R. W. 1986. Small whorled pogonia. Audubon Wildlife Rep. 1986: 780–789. Mehrhoff, L. A. 1989. Reproductive vigor and environmental factors in populations of an endangered North American orchid, Isotria medeoloides (Pursh) Rafinesque. Biol. Conservation 47: 281–296. Mehrhoff, L. A. 1989b. The dynamics of declining populations of an endangered orchid, Isotria medeoloides. Ecology 70: 783–786. Oettingen, S. L. 1992. Small Whorled Pogonia (Isotria medeoloides) Recovery Plan: First Revision. Washington. Paulos, P. G. 1985. Small Whorled Pogonia Recovery Plan. [Newton Corner, Mass.]