Annual or perennial forb to 1.2m tall. Leaves alternating up the stems, 5-20cm long, to 40mm wide, flat, hairless to sparsely hairy, lobed and toothed, with pointed tips. Flower heads cylindrical, .green with yellow florets, and 0 petals, in open groups of often of 20- 100 flower heads per stem at the tops of the stems.
Hybrids between Senecio quadridentatus and Senecio runcinifolius have been recorded from the Murray River near Mildura.
The description above is mostly derived from the description in Thompson, I.R., (2004) Taxonomic studies of Australian Senecio (Asteraceae): 1. The disciform species. Muelleria 19: 154-156, Fig 24 (dried specimen page 155)
Description and photo in G.M. Cunningham, WE Mulham, PL Milthorpe and J H Leigh (1981 and later printings) Plants of Western New South Wales pages 677-678