Banksia sphaerocarpa is a shrub to about 2 metres high. The leaves are narrow linear and up to about 100 mm long. by 1.5 mm wide. The obovoid inflorescences are seen in summer to autumn and are about 9 cm wide at flowering, occurring on short lateral branchlets. They are yellow-brown to orange in colour.
Three botanical varieties are recognised – var. sphaerocarpa, var. caesia and var. dolichostyla:
- var. caesia – larger growth habit than the type and with glaucous (greyish) leaves and smaller seed follicles.
- var. dolichostyla – also with glaucous leaves and small seed follicles but with longer flower parts (perianth and style) than the other varieties.
This species develops a lignotuber and can regenerate by vegetative means from the lignotuber if the upper parts of the plant are destroyed by fire. It can also regenerate from seed.
B.sphaerocarpa has been in cultivation for many years in a range of different forms, some of which have since been described as different species (eg. B.grossa, B.leptophylla). It is best suited to areas with a dry summer and can be difficult to maintain in humid areas. It requires sandy, well drained soils in full sun or partial shade. It is is moderately frost hardy and will tolerate hard pruning once established as it can send up new branches from the lignotuber.
Propagation from seed is reliable without pre-treatment and cuttings also succeed but may be slow to strike and success rate may be well below 100%.
* EPBC Act = Environment Protection and Biodiversity Conservation Act 1999;
ROTAP = Rare or Threatened Australian Plants (Briggs and Leigh, 1988)
For further information refer the Australian Plants at Risk page
Photo: Gwyn Clarke