Flowerheads of senecio mohavensis
may have a few tiny ray florets, but usually contain only yellow disc florets, between 15 and 30, generally rising only a little way above the phyllaries, which number 8 or 13. Phyllaries are hairless, green, fused for most of their length, and equal in length (a third of an inch). Below are three, four or five narrow, linear bractlets. Flowerheads form open, flat-topped arrays.
Plants produce one stem, branching a few times. Stems are green, often tinged with purple. Leaves grow at the base and at even intervals along the stems; they are quite thick, and lined with coarse, irregular lobes, or teeth. Upper leaves are stalkless, with clasping bases, while those lower down are attached by short stalks.