Old flowerheads of Phymaspermum acerosum persist for some time in the neat shallow dome of the stem-tip inflorescence after turning brown in unison.

The protruding stamens and styles are by now ruined, the developmental action departed downwards to the lower seated cypselas where fertilised ovules are morphing into seeds (Pooley, 1998; Onderstall, 1984; iNaturalist).