Flora of North America species comparison

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Ageratina shastensis

Mt. Shasta snakeroot, Shasta ageratina, Shasta snakeroot
Habit 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.
Peduncles

(0–)2–15 mm, puberulent and stipitate-glandular.
Involucres

10–11 mm.
Corollas

white, glabrous.
Phyllaries

apices acute, abaxial faces sparsely puberulent.
Heads

mostly borne singly (each often subtended by a leaflike bract).
Cypselae

hispidulous.
2n

= 34.

Ageratina shastensis
Phenology Flowering Jun–Oct.
Habitat Cracks and crevices of nearly vertical limestone cliffs
Elevation 400–1800 m (1300–5900 ft)
Distribution
from FNA
CA
[BONAP county map]
Discussion

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

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 552.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratina
Sibling taxa
A. adenophora, A. altissima, A. aromatica, A. havanensis, A. herbacea, A. jucunda, A. lemmonii, A. luciae-brauniae, A. occidentalis, A. paupercula, A. rothrockii, A. thyrsiflora, A. wrightii
Synonyms Eupatorium shastense
Name authority (D. W. Taylor & Stebbins) R. M. King & H. Robinson: Phytologia 45: 464. (1980)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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