1. Cunila origanoides (L.) Britton (dittany)

Pl. 433 c, d; Map 1944

Plants perennial herbs, with an often somewhat woody rootstock and short, slender rhizomes. Stems 20–40(–60) cm long, erect or strongly ascending, bluntly (toward the stem base) to relatively sharply 4-angled, several- to numerous-branched, glabrous or sparsely pubescent with short, spreading and/or, crinkly hairs, sometimes mostly along the angles or along 2 opposing, slightly concave sides. Leaves opposite, sessile or nearly so. Leaf blades 1.5–4.0 cm long, 0.7–2.0 cm wide, narrowly to broadly ovate, rounded or occasionally shallowly cordate at the base, angled or tapered to a sharply pointed tip, the margins finely toothed or rarely entire, the surfaces glabrous or sparsely to moderately pubescent along the midvein or main veins with stiff, spreading, multicellular hairs (also sometimes with a few such hairs in the axils of the marginal teeth), also with relatively conspicuous sessile glands. Inflorescences terminal and axillary, dense clusters of 6 to numerous flowers, these short-stalked to nearly sessile (0.5–2.0 mm). Bracts inconspicuous (to 1 mm long), linear to narrowly lanceolate, shorter than the flowers. Calyces 1.5–3.0 mm long at flowering, actinomorphic, lacking a lateral projection, symmetric at the base, funnelform to narrowly bell-shaped, the tube strongly 10-nerved (-ribbed), with a fringe of short, bristly hairs in the mouth, the lobes variously shorter than the tube, narrowly triangular to triangular, not spinescent, glandular on the outer surface, not becoming enlarged or papery at fruiting. Corollas 6–8 mm long, weakly zygomorphic, pinkish purple to lavender or sometimes white, not spotted, the surfaces moderately to densely and minutely hairy, also glandular, the tube funnelform, slightly 2-lipped, the lips up to half as long as the tube, the upper lip notched at the broadly rounded tip, straight or slightly arched, the lower lip 3-lobed, arched to spreading. Stamens 2, strongly exserted, the anthers small, the connective short, the pollen sacs 2, parallel or nearly so, yellowish purple to nearly white. Ovary deeply lobed, the style appearing nearly basal from a deep apical notch. Style not or only slightly exserted, with 2 slender branches at the tip. Fruits dry schizocarps, separating into 2–4 nutlets (rarely the nutlet solitary), this 0.8–1.0 mm long, ellipsoid to ovoid, the surface yellowish brown to brown, glabrous, smooth or very finely pebbled. July–November.

Scattered throughout the Ozark and Ozark Border Divisions, also in portions of the Mississippi Lowlands and the southeasternmost part of the Glaciated Plains (eastern U.S. west to Kansas and Texas). Mesic to dry upland forests, savannas, upland prairies, sand prairies, ledges and tops of bluffs, and banks of streams and rivers; also old fields and roadsides; often on acidic substrates.

The crushed foliage of C. origanoides has a pleasant minty odor and the dried foliage has been used in teas, sachets, and potpourri. Acording to Moerman (1998), Native Americans used the plant as an antiseptic, for pain relief, to lower fevers, and as a tonic. The essential oils sometimes are extracted for medicinal use or for a flavorant in cooking. However, a number of Old World species are extracted commercially more commonly to produce the so-called oil of dittany, including the oregano relative, Origanum dictamnus L., and some members of the genus Dictamnus L. (Rutaceae).

Steyermark (1963) stated that C. origanoides is a desirable ornamental in wildflower gardens and rock gardens. He also noted that the species is noted as a frequent producer of spectacular frost flowers at the end of the growing season. These are formed when sudden overnight freezing temperatures cause the stems to burst, with the resultant release of quantities of sap that are pumped up from the still metabolically active roots. The exuded liquid freezes into intricate layered petal-like or ribbony shapes of ice sometimes more than 5 cm long. This phenomenon was described in fanciful detail by L. F. Ward (1893), who called the plant by the superfluous name Cunila mariana L. and referred to the exudate as frost freaks.