The solitary flowerheads of Cullumia reticulata grow stalkless at stem-tips. Four rows of stiff, hairless involucral bracts are joined at the base. The receptacle is honeycombed.
There is a single row of sterile, yellow ray florets, narrowly elliptic to lanceolate and spreading. They surround a yellow disc of numerous, tiny, bisexual florets.
Flowering happens from before midwinter through spring (Manning, 2007; Bond and Goldblatt, 1984; iNaturalist).