Brachychiton rupestris grows as a succulent tree reaching 10–20 metres (33–66 ft) (rarely 25 metres (82 ft)) in height,[3] though plants in cultivation are usually shorter.[4] The thick trunk is 5–15 metres (16–49 ft) tall, with a 1–3.5 metres (3.3–11.5 ft) diameter at breast height (DBH). It has dark grey bark and is marked by shallow tessellation and deeper fissures. Smaller branches are light green or grey, as are the trunks of immature trees. Like those of all members of the genus, the leaves are alternately arranged along the stems.[3]

B. rupestris is deciduous. Trees in their native habitat are typically leafless between September and December; the timing, duration and extent of leaf drop may be affected by extremes of rainfall or drought.[3] Sometimes trees shed leaves from only some branches.[5] On every tree, the leaves vary in shape, ranging from narrow and elliptic to deeply divided.[6] The upper surface is glossy, contrasting with a pale undersurface. The adult leaf blades are 4–11 centimetres (1.6–4.3 in) long and 0.8–2 centimetres (0.3–0.8 in) wide with pointed (acuminate or apiculate) tips. They have a raised midrib on the upper and lower surface, with 12–25 pairs of lateral veins that are more prominent on the upper surface, arising at 50–60 degrees from the midrib. The compound juvenile leaves have 3–9 spear-shaped (lanceolate) or linear lobes. These each measure 4–14 centimetres (1.6–5.5 in) long and 0.3–1 centimetre (0.1–0.4 in) wide.[3]

Panicles of creamy-yellow flowers with red markings[6] 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 3–8 centimetres (1.2–3.1 in) long, and each flower is 0.5–1 centimetre (0.2–0.4 in) long and 1.3–1.8 centimetres (0.5–0.7 in) wide. The length of the lobes of the perianth is more than half the perianth diameter.[3] Like all Brachychiton species, B. rupestris is monoecious—each plant has distinct male and female flowers.[3] 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.[3]

Groups of 3 to 5 woody boat-shaped follicles,[6] each containing 4 to 8 (or occasionally up to 12) seeds, develop from November to May. The follicles, smooth on the outer surface and hairy inside, split along their length to reveal seeds. The seeds, which are ovoid with a smooth surface, and 6–7 millimetres (0.24–0.28 in) long by 3.5–4.5 millimetres (0.14–0.18 in) wide, are covered by a hairy coating known as the exotesta.[3]

The closely related Proserpine bottle tree (Brachychiton compactus) that occurs only in the vicinity of the town of Proserpine can be distinguished by its more oval leaves, more compact flower heads, and longer ellipsoid follicles.[7] The undescribed Ormeau bottle tree has brighter lime-green new foliage and leaves but is otherwise similar to the Proserpine bottle tree.[8]

Bottle trees are commonly found planted in streets and parks, on farms, and as features in gardens. An avenue in Roma, Queensland, was planted between 1918 and 1920, each tree representing one of 93 local men killed in World War I.[38] The species has been cultivated as an indoor plant and a bonsai subject.[39][40]