Senecio

1. Heads with conspicuous rays clearly exceeding the involucre.

S. vernalis

1. Heads with rays minute (barely equalling involucre) or none.

2. Leaves and stems densely glandular pubescent; bracteoles at base of involucre (2–) 2.5–5.5 mm long.

S. viscosus

2. Leaves and stems glabrate to densely pubescent, but glandular hairs absent or sparse; bracteoles at base of involucre 0.9–2.6 mm long.

3. Rays present but minute, barely equalling involucral bracts; plant densely pubescent, with glandular hairs sometimes present but sparse; bracteoles at base of involucre and involucral bracts usually with greenish tips, rarely dark-tipped.

S. sylvaticus

3. Rays none; plant glabrate to somewhat tomentose, but without glandular-viscid hairs; bracteoles at base of involucre (at least some of them), and often involucral bracts greenish with conspicuous blackish tips. 

S. vulgaris