Flora of North America species comparison

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Senecio serra

butterweed groundsel, sawtooth groundsel, serrated ragwort, tall butterweed, tall ragwort
Habit Perennials, 40–100(–250) cm (caudices ligneous, branched).
Herbage

glabrous or lightly floccose-tomentose proximally when young.
Stems

single or loosely clustered.
Leaves

evenly distributed (proximal often withering before flowering);

petiolate or subsessile;

blades lanceolate or narrowly lanceolate to sublinear, 5–15(–20+) × (1–)1.5–4 cm, bases tapered, margins dentate to subentire (distal leaves smaller, bractlike).
Ray florets

± 5 or ± 8;

corolla laminae 5–10 mm.
Phyllaries

± 8 or ca. 13, 4–9 mm, tips usually green, sometimes black.
Calyculi

of 2–6 linear to filiform bractlets (0.5–5 mm).
Heads

30–90+ in corymbiform to subpaniculiform arrays.
Cypselae

glabrous or glabrate.
2n

= 40.

Senecio serra
Distribution
from FNA
CA; CO; ID; MT; NV; OR; UT; WA; WY
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

Varieties of Senecio serra are distinguished by head size and distribution.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Heads 40–90+; phyllaries ± 8, 4–6 mm; ray florets ± 5, corolla laminae 5–7 mm; disc florets 10–20
var. serra
1. Heads (12–)30–50; phyllaries ± 13, 7–9 mm; ray florets ± 8, corolla laminae 7–10 mm; disc florets 20–40+
var. admirabilis
Source FNA vol. 20, p. 566. Treatment author: Theodore M. Barkley†.
Parent taxa Asteraceae > tribe Senecioneae > Senecio
Sibling taxa
S. actinella, S. amplectens, S. ampullaceus, S. aphanactis, S. arizonicus, S. aronicoides, S. astephanus, S. atratus, S. bigelovii, S. blochmaniae, S. californicus, S. cannabifolius, S. clarkianus, S. crassulus, S. elegans, S. elmeri, S. eremophilus, S. ertterae, S. erucifolius, S. flaccidus, S. fremontii, S. hydrophiloides, S. hydrophilus, S. integerrimus, S. jacobaea, S. lemmonii, S. lugens, S. lyonii, S. megacephalus, S. mohavensis, S. multidentatus, S. neowebsteri, S. parryi, S. pattersonensis, S. pseudoarnica, S. pudicus, S. quaylei, S. rapifolius, S. riddellii, S. sacramentanus, S. scorzonella, S. sheldonensis, S. soldanella, S. spartioides, S. sphaerocephalus, S. spribillei, S. squalidus, S. sylvaticus, S. taraxacoides, S. triangularis, S. viscosus, S. vulgaris, S. warnockii, S. wootonii
Subordinate taxa
S. serra var. admirabilis, S. serra var. serra
Name authority Hooker: Fl. Bor.-Amer. 1: 333. (1834)
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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