Clinopodium arkansanum (Nutt.) House

Arkansas Calamint

Clinopodium arkansanum plant

Family - Lamiaceae

Stems - Multiple from the base, erect to ascending, from fibrous roots, 4-angled, typically purple at the base and nodes, glabrous, branching, to +/-15cm tall, herbaceous, glandular punctate (use a lens to see). Entire plant has a strong mint fragrance.

Clinopodium arkansanum stemStem

Leaves - Opposite, decussate, sessile, linear to linear-spatulate, to 1.5cm long, 3mm broad, entire, glabrous, rounded to subacute at the apex, densely glandular punctate on both surfaces.

Inflorescence - Single axillary flowers. Pedicels to +/-5mm long, glabrous.

Clinopodium arkansanum inflorescenceFlowering branch

Flowers - Corolla purplish (very rarely all white), bilabiate, 1.2cm long, pubescent externally, contracted and brown at the base in the calyx-covered portion. Upper lip single-lobed. The lobe deflexed, 3-4mm broad, 2-3mm long, emarginate. Lower lip 3-lobed. Lobes rounded, 2mm long and broad. The center lobe slightly larger than the laterals. Stamens 4, didynamous, 2 attached in the basal 1/4 of the corolla tube, 2 attached in the apical 1/4 of the corolla tube and slightly exserted. Filaments whitish and glabrous, to +3mm long. Anthers lilac, bilobed, 1mm long. Style white (lilac at the apex), glabrous, to 1cm long. Stigma unequally 2-lobed. Ovary green, glabrous, deeply 4-parted, .5mm long. Calyx bilabiate. Calyx tube to 4mm long, glandular punctate, with 13 ribs, greenish-purple. Upper lip 3-lobed. Lobes acuminate, 1.1-1.2mm long. Lower lip 2-lobed, lobes equal or slightly longer than upper lobes, acuminate. Calyx with a ring of floccose hairs at the summit of the tube internally.

Clinopodium arkansanum flower

Clinopodium arkansanum calyxCalyx.

Flowering - May - October.

Habitat - Limestone glades and knobs, rocky open ground, wet meadows along spring branches, gravel bars, bluffs escarpments.

Origin - Native to U.S.

Other info. - This little species is very common in the Ozarks of Missouri. The plant is more often smelled than seen. Plant hunters strolling through the glades of Missouri often step on the plant releasing a very strong mint aroma into the air. The smell is pleasant and unmistakable. Because the plant has thin stems and thin leaves it often gets overlooked until that fragrance fills the air. Chewing on the plant gives you fresh breath that will last for hours.

Photographs taken off Hwy 106, Shannon County, MO., 6-23-03 (DETenaglia); also near White Ranch Conservation Area, 6-3-2017 (SRTurner).