Habenaria herbiola R. Brown in W. Aiton and W. T. Aiton, Hortus Kew. 5: 193. 1813; H. flava (Linnaeus) R. Brown var. herbiola (R. Brown) Ames & Correll

Inflorescences rather dense, stout (in part from floral bracts usually long, often greatly exceeding flowers); lip (excluding auricles) oblong, obtuse or rarely emarginate, rarely triangular and acute. 2n = 42.

Flowering May--Aug. Alluvial forests, riparian thickets, wet meadows, wet prairies, seeps, salt marshes; 0--900 m; N.B., N.S., Ont., Que.; Ark., Conn., Del., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Tex., Vt., Va., W.Va., Wis.

Tuberoids and the over-wintering bud typically form at a marked distance from the parent shoot, resulting in clonal colonies dominated by sterile plants.

The southern Platanthera flava var. flava and the northern var. herbiola are very distinct in their extreme forms, but they seem to intergrade, at least in the herbarium. They are usually as readily distinguished by plant habit as by lip shape. The slender, laxly flowered habit of the former is compounded by usually short floral bracts, whereas in the latter bracts are typically longer than the flowers and often exceed them, adding to the congested and broader aspect of the inflorescence. Further complicating determination are a few specimens from the region from the southern tip of Lake Michigan south and southwestward. Those have markedly triangular lips with prominent triangular auricles or basal lobes. These stout but rather laxly flowered plants seem to occupy mesic wooded slopes and may constitute a distinct taxon; comparisons should be made with similar Asiatic species.