Brachychiton rupestris

Brachychiton rupestris.

The Queensland or Narrow-leaved Bottle Tree was previously Sterculia rupestris.
Endemic to Queensland it is commonly seen in parks, streets and gardens in Brisbane.

Young trees have straight trunks that gradually expand up to 3.5 m across.
This is due to water stored under the bark.
Young trees have greyish-green trunks and branches.
On older trees the dark grey bark is tessellated and fissured.
Partly or fully deciduous in spring they can be up to 25 m high but are mostly less.

Leaves are alternately arranged in a spiral.
Stipules, covered in stellate hairs, are only a few mms long.
Juvenile leaves can be elliptic or liner and up to 15 cm long.
Others are deeply divided into 5 (3 to 9) linear or lanceolate lobes.

Adult leaves are mostly narrowly elliptic.
They are up to 13 cm long and 2 cm wide.
On petioles up to 3 cm long the tips are pointed or bristle-like.
There are no hairs and the underside is paler.
The midrib is raised on both surfaces and the edges are shallowly scalloped.

Axillary inflorescences are branched clusters up to 8 cm long.
Each has up to 30 flowers.
Trees have both male and female flowers.
The flowers, without petals or nectaries, are on short stalks.
All flowers have a short androgynophore.

The bell-shaped calyx tube, with 5 lobes, is up to 1 cm long.
The sepals are cream with red markings on the inner surface of the lobes.
There are dense stellate and glandular hairs inside and a few externally.

Male flowers have 15 stamens with filaments mostly fused into a staminal column.
The 1.5 mm long yellow anthers are at the top surrounding the rudimentary ovaries.
Female flowers have 5 separate ovaries with one 1.5 mm style and 5 stigmas.
There are glandular hairs on the ovary and 1 mm high staminodes around the base.

The fruit are woody follicles up to 3 cm long on stalks half that length.
There is a short curved beak at the tip.
They are smooth outside and lined with stellate hairs inside.
There are around 6 seeds (4 – 12) smooth seeds.
Each seed is surrounded by a thin layer covered with bristles.