Collinsonia canadensis L.

Richweed, Horse Balm

Collinsonia canadensis plant

Family - Lamiaceae

Habit - Perennial forb with short, thick, woody rhizomes.

Stems - Strongly ascending to erect, to 1 m, 4-angled, mostly unbranched, glabrous or sparsely and inconspicuously pubescent.

Collinsonia_canadensis_stemStem and node.

Leaves - Opposite, petiolate, simple, ovate or elliptic, sharply pointed, toothed or scalloped, upper surface glabrous or sparsely pubescent, underside sparsely to moderately short-hairy and with sessile glands.


Inflorescences - Terminal pyrimidal panicles with open, racemose branches, with flowers 2 per node on short stalks. Bracts to 3 mm, lanceolate.



Flowers - Calyces 2.5-5.0 mm long, somewhat zygomorphic to nearly actinomorphic, bell-shaped, 15-nerved, glabrous in the mouth, usually slightly 2-lipped, the lobes minutely hairy and glandular on both surfaces, becoming enlarged and papery at fruiting. Corollas 12-15 mm long, zygomorphic, mostly yellowish, sometimes with dull purple to reddish brown markings, the surfaces glandular and pubescent, the tube funnelform, 2-lipped to about the midpoint, the upper lip shorter, the 4 lobes spreading to loosely ascending, with entire margins, the lower lip prominent, spreading, 1-lobed, this strongly fringed, mostly white. Stamens 2, strongly exserted and somewhat spreading. Ovary deeply lobed, the style appearing nearly basal. Style strongly exserted, with 2 slender branches at the tip.



Fruits - Dry schizocarps, usually consisting of a solitary globose nutlet to 2.5 mm diameter, this glabrous, smooth and shiny, brown.

Flowering - July - September.

Habitat - Forests, streambanks.

Origin - Native to the U.S.

Lookalikes - None.

Other info. - This striking and unmistakable species is found in Missouri mostly in the eastern half of the Ozark Division. Missouri lies at the far western extent of the plant's natural range, which extends eastward to coastal areas and also into Canada. The flowers are beautiful in intricate detail, with deeply fringed lower petal lips and strongly exserted stamens and style. The inflorescence emits a pleasant lemony fragrance. Steyermark noted that the roots have been used to alleviate kidney ailments, and numerous medicinal applications were practiced by Native Americans.

Photographs taken at Johnson's Shut-Ins State Park, Reynolds County, MO, 8-20-2013; also at Royal Gorge near Ketcherside Mountain, Iron County, MO, 8-26-2016 (SRTurner).