Ageratina shastensis

(D. W. Taylor & Stebbins) R. M. King & H. Robinson

Phytologia 45: 464. 1980.

Common names: Mt. Shasta snakeroot
Basionym: Eupatorium shastense D. W. Taylor & Stebbins Madroño 25: 218, fig. 1. 1978
Treatment appears in FNA Volume 21. Treatment on page 552. Mentioned on page 548, 553.

Perennials, 15–45 cm (bases woody, enlarged, occasionally rhizomatous). Stems erect (clustered from bases), puberulent to pubescent (often with some glandular hairs distally). Leaves opposite proximally, alternate on at least distal 1/2 of stems; petioles 4–6 mm; blades (venation raised-reticulate) orbiculate (juvenile) or deltate-ovate, 1.5–3 × 1–2 cm, (subcoriaceous) bases obtuse to truncate, margins entire or coarsely serrate to dentate, apices acute to acuminate, abaxial faces ± gland-dotted and/or stipitate-glandular. Heads mostly borne singly (each often subtended by a leaflike bract). Peduncles (0–)2–15 mm, puberulent and stipitate-glandular. Involucres 10–11 mm. Phyllaries: apices acute, abaxial faces sparsely puberulent. Corollas white, glabrous. Cypselae hispidulous. 2n = 34.

Phenology: Flowering Jun–Oct.
Habitat: Cracks and crevices of nearly vertical limestone cliffs
Elevation: 400–1800 m


Ageratina shastensis is recognized by relatively large solitary heads and coarsely serrate, subcoriaceous leaves alternate on distal parts of stems.

Selected References


Lower Taxa