Shrubby Thoroughwort

Perennials or subshrubs (shrubs), 60–100 cm. Stems mostly sparse­ly puberulent (hairs upcurved or apically bent). Leaves mostly opposite, sometimes subopposite to alternate on distal ¹/3 of stems; petioles 2–8(–12) mm; blades lanceolate, mostly 3–8(–11) × 1–3 cm, bases rounded, margins entire or shallowly crenate, apices acuminate, abaxial faces eglandular, adaxial glabrous. Involucres 4.5–5.5 mm. Phyllaries: outermost narrowly lanceolate, glabrous, margins hyaline on proximal ²/3, eciliate. Corollas usually white, sometimes purple-tinged to yellowish, 2.5–3 mm, lobes glandular. Cypselae 1.8–2.8 mm, sparsely hispidulous. 2n = 20.

Eupatorium solidaginifolium A. Gray, Smithsonian Contr. Knowl. 3(5): 87. 1852

Koanophyllon solidaginifolium, the shrubby umbrella thoroughwort, is a plant species native to Arizona, western Texas, New Mexico, Chihuahua, Coahuila, Durango, Jalisco, and Zacatecas. It grows primarily on canyon walls, ledges, and other stony outcrops.

Koanophyllon solidaginifolium is an herb or subshrub up to 100 cm (39 inches) in height. Leaves are lanceolate with rounded bases and narrow pointed tips. Flowers are usually white, but sometimes tinged with purple or yellow.