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large-head groundsel, rocky ragwort

Habit Perennials, (15–)30–50 cm (rhizomes woody, suberect or creeping).
Herbage

loosely arachno-tomentose, unevenly glabrescent.

Stems

single or clustered.

Leaves

progressively reduced distally; weakly petiolate;

blades lanceolate to narrowly oblanceolate, 10–18+ × 1–2(–3+) cm, bases tapered, margins entire or wavy (often with dark, cartilaginous denticles; mid leaves similar, smaller, sessile; distal leaves bractlike).

Ray florets

± 13;

corolla laminae (5–)15–20 mm.

Phyllaries

± 21, 9–12(–14) mm, tips not notably blackened (short-hairy).

Calyculi

of 5–8+ linear to filiform bractlets (lengths 1/2–7/8+ phyllaries).

Heads

usually 1 (sometimes subtended by 1–2 smaller heads).

Cypselae

glabrous.

2n

= 40.

Senecio megacephalus

Phenology Flowering summer.
Habitat Rocky, moist or drying sites, especially on mountain slopes
Elevation 1500–2500 m (4900–8200 ft)
Distribution
from FNA
ID; MT; WY; AB; BC
[BONAP county map]
Source FNA vol. 20, p. 553.
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. mohavensis, S. multidentatus, S. neowebsteri, S. parryi, S. pattersonensis, S. pseudoarnica, S. pudicus, S. quaylei, S. rapifolius, S. riddellii, S. sacramentanus, S. scorzonella, S. serra, 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
Name authority Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 410. (1841)
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