A tree capable of reaching 20 metres tall in the wild (although such trees will be old) and a canopy spread to 10 m. It is one of the iconic and easily identifiable banksias of the east coast of Australia.
It grows along most of the entire coast of NSW, extending into the central tablelands (Blue Mountains area), extending north to the Sunshine Coast in Qld and south to Victoria and Tasmania.
It is a common tree on sandstone outcrop and sandy soils, in dry sandstone ridgetop woodland and gully forest. Also grows in sandy coastal heath and shrublands. Not usually found on other soil types. The bark has a distinctive warty, gnarled appearance.
The leaves are alternate to whorled, and with a leather, almost-plastic texture, oblong to narrow-obovate, to 20 cm long and 4 cm wide. The lower surface is much paler than the mid green upper surface. The conspicuous feature is the serrated leaf margin.
The inflorescences of banksias are generally referred to as spikes or a spike-like structure which consists of fused racemes of paired flowers (hence it gets referred to as a conflorescence). There can be 100s of flowers in each spike. The flowers of banksias have 4 tepals (petals or sepals) in a tubular formation, 4 anthers hidden inside and an elongated carpel (female part) where the style extends outwards forming the edge of the spike (somewhat similar to individual grevillea and hakea flowers).
In this species, the spikes are generally to 20 cm long (this author has observed up to 40 cm in the field on old plants) and about 10 cm wide, with each flower thin but up to 5 cm long, yellow to creamy-green in colour.
The spike then turns into a cone-like structure of follicles; a fruit which splits open on one side. Each follicle has one or two winged seeds which is actually a fruit in itself called a samara. The follicles can take a long time to mature and open, usually needing a fire. Each “cone” can produce a fair amount of seed. In this species, follicles are about 3 cm long.
A somewhat hardy tree in the right spot and on the right soil – sandy and free draining. This author is noticing this species getting planted more often as replacement street trees in Sutherland Shire.
Plant in a sunny spot with good drainage, on a slight slope works really well. Do not mulch too heavily and try to keep the grass away from the trunk. Very hardy once established.
Slow growing but will grow consistently if happy and will form a very nice shrub after a few years. May grow to 10 m in a garden (although this will take time) so allow some space. Very suitable for sandstone-outcrop gardens.
Do not apply a high phosphorus fertiliser as Proteaceae are generally sensitive.
Prune after flowering or harvest cut flowers. Can be trained into a denser shape with periodic pruning.
Susceptible to Phytophthora and any other root rotting fungus.
Propagation from seed is very reliable and not too difficult.
Can regenerate from seed bank after fire very readily as well as epicormic shoots and a lignotuber below ground.
Banksia is a now a genus of about 170 species (with the inclusion of the genus Dryandra) occurring in Australia but also 1 species in New Guinea and the Aru Islands Regency. NSW currently has about 16 species.
Banksia – named in honour of Joseph Banks (1743 – 1820), famous naturalist and botanist on the Endeavour and other expeditions, and President of the Royal Society for over 40 years. The genus was named in his honour by Linnaeus filius (Carl von Lynne – the Younger, son of the famous Carl von Lynne (Linnaeus)).
serrata – from the Latin serra which means “knife” or “saw” (root of “serrated”) referring to the serrated leaf margins.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Banksia serrata profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Banksia~serrata
Gardening with Angus – Banksia serrata profile page https://www.gardeningwithangus.com.au/banksia-serrata-old-man-banksia/
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.