Senecio vulgaris is an annual herb, summer or winter, 10-40 cm, from a taproot, stems leafy, branching, young plant somewhat cobwebby, later almost hairless.
Leaves alternate, hairy somewhat fleshy, narrow, irregularly, pinnately lobed 2-10 cm long, 0.5-4.5 cm wide, lobes toothed, lower leaves tapering to a stalk, upper leaves stalkless, clasping stem.
Flowers yellow, all tubular, no rays, heads 0.8-1 cm high, cylindrical, higher than wide, outer bracts very short, usually black-tipped, inner bracts linear, black-tipped, almost as long as flowers; bristles of achene longer than flowers, heads in branched clusters, self-fertile (autogamous), but visited by some insects (Mulligan and Kevan 1973; Robinson et al. 2003); blooming May-Oct.
Fruit dry achenes white-plumed, wind dispersed.
Wetland status: FACU.
Frequency in NYC: Occasional.
Origin: Old world.
Habitat: Open areas, lawns, roadsides, edges, fill, soil pH 5-8.5; Intolerant of drought, salt, fire and heat (USDA, NRCS 2010).
Notes: Plants eaten by rabbits and other small herbivores. Contains toxic pyrrolizidine alkaloids (Uva et al. 1997). Some insects accumulate these toxins which discourages predators; historically groundsel has been used as a medicine (Robinson et al. 2003).