Perennial herb 10 - 65 cm tall Leaves: opposite, stalkless, dark green, 1.5 - 12 cm long, 3 - 30 mm wide, one- to three-nerved (rarely five-nerved), non-toothed, but with short bristles along the edges. The leaf shape is quite variable, ranging from linear to elliptic, or inversely egg-shaped, but usually widest near the middle, possibly blunt-tipped, but never long-pointed. Inflorescence: of one to eight, erect flowers clustered at the the stem apex, but on some larger stems often also in clusters at the ends of very short branches from the upper one to ten nodes. The terminal inflorescence is normally subtended by a pair of large, leaf-like bracts. Flowers: blue (at least above the middle), 3 - 5 cm long, more or less radially symmetric, usually opened at least slightly, and subtended by a pair of inversely lance-shaped to linear bracts. The flowers are usually inflated or swollen unequally along one side, but otherwise appearing much like elongate eggs. Sepals: five, but fused for at least half their length into a 0.5 - 1.5 cm long tube, then separating into narrowly inversely lance-shaped (widest above middle), 0.4 - 1.7 cm long, 0.8 - 5 mm wide lobes with bristly-hairy edges. Petals: five, but fused with somewhat shorter membranes (plaits) between the incurved, 3 - 8 mm long, 3.5 - 6 mm wide, rounded, wide based lobes with abruptly pointed tips. The separate portion of the petal lobes typically do not reach more than 2 mm beyond the 2 - 6.5 mm long, erect, somewhat two-cleft, toothed or fringed plaits. The base of the petal tube is greenish white with green veins, but upwards it turns more blue, with the petal lobes and plaits striped with deep blue. Occasionally the blue parts are more pale violet. Stamens: five, attached to the inside of the petal tube, the filaments 1 - 1.5 cm long, with the anthers fused together. Pistil: with a single-chambered, superior ovary; a short, stout style; and a two-lobed stigma. There is a whorl of nectar glands present around the base of the ovary, though they are not attached to the fused petal tube base. Fruit: a single-chambered, two-valved, elliptic capsule with numerous seeds. Stems: one to seven, erect or somewhat decumbent, normally unbranched, hairless, or occasionally with short hairs. Seeds: flattened, winged, and smooth.
Similar species: Gentiana saponaria has often been confused with a more southeastern species, G. catesbaei, but that species has brighter green, wider leaves, which are widest near the base, not the middle. Also, G. catesbaei has sepal lobes longer than the tube, and the petal lobes are usually 2 - 4 mm longer than the alternating plaits. Gentiana saponaria is also often confused with a hybrid, G. x billingtonii, which is a cross between G. puberulenta and G. andrewsii. The hybrid however, tends to have leaves and sepal lobes widest near the base, the leaves tend to be stiffer and lighter green in color, and the flowers appear to be a deeper color blue. The species and two subspecies of G. andrewsii may also be confused with G. saponaria, but their leaves are much wider with long pointed tips, and the tiny petal lobes are obviously shorter than the fused, fringed plaits, which form the top of the closed flower.
Flowering: September to mid-November
Habitat and ecology: Overall rare in our area, but primarily in sandy moist prairies and Black Oak savannas, moist or seasonally wet thickets, open woods, or even along railroad tracks.
Occurence in the Chicago region: native
Notes: This species is now extirpated (extinct) in Michigan. The species has a relatively wide distribution in the United States, and much physical variation occurs between different populations, as well as within single populations (Pringle 1967).
Etymology: Gentiana is named after Gentius, king of Illyria, who supposedly discovered a medicinal value for the yellow gentian. Saponaria refers to the resemblance of the leaves to the common soapwort, which is in the genus Saponaria.
Stems 2-7 dm, glabrous or occasionally papillate-puberulent; lvs linear to elliptic or obovate, mostly 5-10 cm, scabro-ciliolate; fls few-several in a dense terminal cluster and 1-few in the upper axils or on short lateral branches; cal-tube glabrous, the lobes ciliolate, usually narrowly oblanceolate, shorter than to about as long as the tube; cor blue at least distally, 3-5 cm, ventricose, narrowly open, the lobes usually incurved above, rounded, seldom surpassing the bifid plaits by more than 2 mm; anthers connate; 2n=26. Moist woods and thickets; s. N.Y. to Fla., w. irregularly to Ill., Ark., e. Okla., and e. Tex. Sept., Oct. (G. cherokeensis; Dasystephana latifolia)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.