Perennial herb 20 cm - 1 m tall Stem: erect, unbranched below inflorescence, with long gland-tipped and bristly hairs (at least at the nodes), four-angled with narrow, but obvious, wings on angles. All four sides of the stem are about the same width and have almost flat to slightly rounded (convex) faces, which gives the stem an appearance of being almost square in cross section. Leaves: opposite, stalkless, 2 - 7 cm long, about one-third to one-half as wide as long, egg-shaped to widely lance-shaped, shallowly toothed, sometimes glandular-bristly on one or both sides, and with three almost parallel lengthwise veins running upward from base of leaf. Flowers: stalked, rose-lavendar, over 1 cm tall, showy, radially symmetric, and arranged in terminal, short-branched clusters. The flowers have a long, fused, basal "sepal-petal tube" (hypanthium) and four spreading lobes. Sepals: hairless or bristly-hairy, four, but fused for over half their length and also fused with petal bases into a 0.7 - 1 cm long hypanthium, then separating into four, 2 - 4 mm long, ascending, narrowly triangular lobes with pointed tips. Petals: often bristly on outside, four, but fused at base and fused with sepals into a 0.7 - 1 cm long hypanthium, then separating into four, spreading, 1.5 - 2 cm long, somewhat egg-shaped lobes with blunt tips. Stamens: eight, with slender twisted filaments, and golden-yellow, 5 - 7 mm long, single-chambered, elongate-linear, curved anthers with a short, fragile, spur-like appendage underneath, on opposite side of filament attachment point. The anthers, which open by a single pore at the tip, are prolonged about 0.5 - 1 mm behind the point of attachment to the filaments, and are arranged on one side of the flower due to the twisting of the filaments. Pistil: with one, three- to five-chambered, inferior ovary; and a single, terminal, slender style with a rounded stigma at the apex. Fruit: a many-seeded, rounded capsule which is enclosed by the urn-shaped remnant hypanthium which has a constricted tubular neck and flaring remnant sepal tips. Seeds: many per capsule, coiled like a snail shell, and lacking endosperm. Roots: fibrous, though often tuberous-thickened.
Similar species: Rhexia virginica is our only species in this genus and family in the Chicago Region, but in southern Indiana two other species of Rhexia occur. The more similar of those two species, R. interior, differs by having the stem angles only scarcely winged or not at all winged, thus the stem appears more square in cross section, plus the stem, leaves, and hypanthium are much more bristly and stiff-hairy. The other species, R. mariana, has stem sides that are quite dissimilar, with two opposing sides being broad, dark green, and convex, while the other two opposing sides are much narrower, pale, and concave. Perhaps another superficially similar taxon to R. virginica in the Chicago Region is Sabatia angularis, but that species has more pale flowers (light rosey-pink) with five sepals and petals, non-toothed leaves that often clasp the stem, and light green or straw-colored stems that are normally bushy with many opposite branches above.
Flowering: late June to late September
Habitat and ecology: Not too common, localized to sterile sandy or peaty soils, especially in the eastern half of the Chicago Region.
Stems 2-10 dm from an often tuberous-thickened, otherwise fibrous-rooted base, subequally quadrangular and evidently winged, usually ±bristly at the nodes, otherwise bristly to glabrous; lvs ovate to lance-ovate, 2-7 cm, usually a third to half as wide, sometimes bristly on one or both sides; hypanthium smooth or bristly, 7-10 mm at maturity, the neck mostly shorter than the body; sep narrow, acute or acuminate, 2-4 mm; pet rose-lavender, 15-20 mm, often bristly on the back; anthers 5-7 mm; 2n=22, 44. Moist, open places; N.S. to Wis., s. to Fla. and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.