Closeup of spherical golden yellow bloom made up of hundreds of individual flowers
var. caesia, Bendering Reserve
Banksia sphaerocarpa is a widely distributed Western Australian species with four (or five if one includes var. dolichostyla) varieties:
B. sphaerocarpa var. caesia, first described by Alex George in his 1981 revision of the genus, grows larger than most other varieties, reaching 2 m (6.6 ft), or occasionally 4 m (13 ft), in height. It has yellow blooms and bluish grey foliage and is found in the central and southern Wheatbelt between the towns of Piawaning, Kojonup, Newdegate and Corrigin.[2]
B. sphaerocarpa var. dolichostyla (Ironcap Banksia) was first described by Alex George in his 1981 revision of the genus. It is the largest of the varieties, encountered as a large shrub or small tree to 4 m (13 ft) high. It is larger in all parts than the other varieties, and has been considered a separate species. It is restricted to a small area from South Ironcap, east of Hyden, south to Mt Holland in the eastern Wheatbelt.[2]
B. sphaerocarpa var. latifolia was originally described in a manuscript by Mueller and published by Bentham in 1870. It grows as a small rounded shrub to 50 cm (1.6 ft) in height, and is restricted to the vicinity of the south coast between Denmark and the Porongorup Range, where it is found in low, open forest of Eucalyptus marginata and E. calophylla.[3]
B. sphaerocarpa var. sphaerocarpa is widely distributed from the Darling Plateau east of Perth to the Whicher Range in the southwest, and southeast to the Stirling Range. Populations north of Perth once referable to it are now classified as var. pumilio.[3]
B. sphaerocarpa var. pumilio, first described by Alex George in 2008, is a small shrub less than a metre high. It is found from Tathra National Park east of Eneabba south to the Chittering valley. Its subspecific name is derived from the Latin pumilio "small", relating to the flowers.[3]