Senecio mohavensis
Senecio riddellii
Mohave groundsel, Mojave ragwort
Riddell's groundsel, Riddell's ragwort
(sometimes purple-tinged) glabrous.
glabrous.
usually 1 (freely branching upward).
usually multiple (branching upward).
equally distributed; petiolate;
blades ovate to obovate, 2–6 × 0.5–2(–4) cm, bases tapered, margins coarsely lobed or irregularly dentate (mid and distal leaves similar, bases expanded, truncate to cordate, clasping, 1–2 cm across).
± evenly distributed (proximal often withering before flowering, pendulous);
sessile or obscurely petiolate;
blades linear-filiform (or irregularly pinnately divided into linear-filiform lobes), blades or lobes 4–9 cm × 1–5 mm, bases ± linear, ultimate margins entire.
0 or 1–3+;
corolla laminae 0.1–1 mm (little expanded, barely, if at all, surpassing phyllaries; sometimes laminae 0 and heads perhaps technically disciform).
± 8;
corolla laminae (often falling early) 8–10 mm.
± 8 or ± 13, 6–7 mm, tips green.
± 13, 7–10(–12+) mm, tips green.
of 3–5+ lance-linear bractlets.
usually of 3–8+ lance-linear to filiform bractlets (lengths 1/10–1/3 phyllaries).
3–10 in loose, cymiform arrays.
5–20+ in close, corymbiform arrays (involucres campanulate, 7–10 mm diam.).
hairy.
hirtellous.
= 40.
= 40.
Senecio mohavensis
Senecio riddellii
Senecio mohavensis is similar to S. flavus (Decaisne) Schultz-Bipontinus of the Mediterranean region and southwest Asia, which raises phytogeographic questions (cf. A. Liston et al. 1989; Liston and J. W. Kadereit 1995; M. Coleman et al. 2001). The last cited study showed that a previously recognized variety of S. flavus is more closely related to S. mohavensis than to S. flavus and a new combination was made: S. mohavensis subsp. brevifolius (Kadereit) M. Coleman.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Senecio riddellii intergrades morphologically with S. spartioides. Typically, the former has larger heads with campanulate involucres 7–10 mm diam.; the latter has cylindric involucres rarely more than 6 mm diam.
Senecio riddellii is poisonous to livestock. It is now locally scarce because of efforts to eradicate it.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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