Narrow-leaved bottle tree (Brachychiton rupestris)

Description

Brachychiton rupestris, commonly known as the narrow-leaved bottle tree or Queensland bottle tree, is a tree in the family Malvaceae native to Queensland, Australia. Discovered and described by Sir Thomas Mitchell and John Lindley in 1848, it gained its name from its bulbous trunk, which can be up to 3.5 metres (11 ft) diameter at breast height (DBH). Reaching 10–25 metres (33–82 ft) high, the Queensland bottle tree is deciduous, losing its leaves between September and December. The leaves are simple or divided, with one or more narrow leaf blades up to 11 centimetres (4 in) long and 2 centimetres (0.8 in) wide. Cream-coloured flowers appear from September to November, and are followed by woody boat-shaped follicles that ripen from November to May. No subspecies are recognised. As a drought-deciduous succulent tree, B. rupestris adapts readily to cultivation and is tolerant of a range of soils and temperatures. It is a key component and emergent tree in the endangered central semi-evergreen vine thickets—also known as bottletree scrub—of the Queensland Brigalow Belt. Remnant trees are often left by farmers on cleared land for their value as shade and fodder trees. Brachychiton rupestris grows as a succulent tree reaching 10–20 metres (33–66 ft) (rarely 25 metres (82 ft)) in height, though plants in cultivation are usually shorter. 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. 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. Sometimes trees shed leaves from only some branches. On every tree, the leaves vary in shape, ranging from narrow and elliptic to deeply divided. 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.