Many flowerheads of Athanasia tomentosa grow densely together in a branched, corymb-shaped, stem-tip inflorescence.

The tiny yellow disc florets comprising one flowerhead are closely bunched in their involucre, a cup formed of a few rows of grey-green bracts upon a receptacle, the flowerhead base. Each floret is five-lobed and bisexual. There are no ray florets in Athanasia. A flowerhead or capitulum is less than 5 mm in diameter.

These plants flower in summer. The photo was taken in January (Vlok and Schutte-Vlok, 2010; Leistner, (Ed.), 2000; iSpot).