The flowerheads of Senecio spiraeifolius are produced in nearly flat to shallowly domed, many-flowered inflorescences on branched stalks. The yellow rays are more flexed back than spreading around the prominent yellow disc.

A flowerhead measures from 15 mm to 18 mm across. The green involucre is regularly ribbed in pronounced fashion. In bud phase it is wider at the top. Later, when fruiting, it is narrower at the top.

Flowering happens from midwinter to early spring (Manning and Goldblatt, 1997; Bond and Goldblatt, 1984; iNaturalist).