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FNA | Family List | FNA Vol. 21 | Asteraceae | Ageratina

12. Ageratina shastensis (D. W. Taylor & Stebbins) R. M. King & H. Robinson, Phytologia. 45: 464. 1980.

Mt. Shasta snakeroot

Eupatorium shastense D. W. Taylor & Stebbins, Madroño 25: 218, fig. 1. 1978

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.

Flowering Jun–Oct. Cracks and crevices of nearly vertical limestone cliffs; 400–1800 m; Calif.

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


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