Koanophyllon palmeri (A. Gray) R. King & H. Rob.

Koanophyllon palmeri is native primarily to western Mexico (Sinaloa, Chihuahua, and Sonora to Durango and Jalisco; R. McVaugh 1984; B. L. Turner 1997). Similar plants (known as Eupatorium palmeri var. tonsum B. L. Robinson) occur in near-coastal localities from Michoacan to Colima, Jalisco, Nayarit, and Sinaloa, Mexico.

Perennials or subshrubs, 50–150 cm. Stems mostly sparsely puberulent (hairs upcurved or apically bent). Leaves opposite; petioles 0–5 mm; blades lanceolate to triangular-lanceolate, (2–)3–6 × 0.8–2 cm, bases rounded, margins shallowly serrate to subentire, apices acute (not acuminate), abaxial faces eglandular or minutely gland-dotted, adaxial sparsely strigose to hispidulous. Involucres (3–)3.5–4 mm. Phyllaries: outermost ovate-elliptic to obovate to narrowly oblong-lanceolate, puberulent, margins herbaceous, usually weakly ciliate. Corollas white, (2–)2.4–2.8 mm, lobes glandular. Cypselae 1.6–1.8 mm, sparsely hispidulous.

Eupatorium palmeri A. Gray, Proc. Amer. Acad. Arts 21: 383. 1886

Koanophyllon palmeri, called Palmer’s umbrella thoroughwort, is a North American plant species in the family Asteraceae. It is native to Arizona, southwestern New Mexico, and western Mexico from Sonora as far south as Michoacán.

Koanophyllon palmeri 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.