Panicles of creamy-yellow flowers with red markings appear from September to November in the species' native range. These arise from axillary buds on end branches. Each panicle contains 10–30 flowers and is long, and each flower is long and wide. The length of the lobes of the perianth is more than half the perianth diameter. Like all "Brachychiton" species, "B. rupestris" is monoecious—each plant has distinct male and female flowers. Male flowers have 15 stamens, with pale yellow anthers, while female flowers have cream or white stigmas surrounded by rudimentary stellate (star-shaped) carpels, which sit atop the ovaries.