Banksia oblongifolia

Fern-leaved Banksia

Family: Proteaceae

A shrub to 3 m tall with a lignotuber. It is found usually on sandstone and sandy soils, as well as sandy alluvium.

It is found mainly along the NSW coast, to as far south as Ulladulla, extending north into the central tablelands (where few records are indicated) then up the north coast into Queensland to about the Sunshine Coast, growing mainly in dry sclerophyll woodlands and forests as well as coastal heath and shrublands.

The leaves are alternate to pseudo-whorled, somewhat stiff and leathery, obovate to oblong, to 8 cm long and 2 cm wide with toothed margins. Olive to blue-green on upper surface and white on under surface, sometimes with with brown hairs on mid and secondary veins. New leaves can be a brilliant brown-red which adds interest.

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 and extends outwards forming the edge of the spike (somewhat similar to individual grevillea and hakea flowers).

In this species, the spikes are generally to 15 cm long and up to 5 cm wide, with each flower thin but up to 2.5 cm long, pale yellow to green-yellow, with the developing buds often tinged grey-blue (a useful identification feature).

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 or a drying out period. Each “cone” can produce a fair amount of seed with this species having follicles to 20 mm long with up to 80 follicles per “cone”.

Susceptible to Phytophthora and any other root rotting fungus.
Propagation from seed is very reliable and not too difficult.

In the garden

Not as popular as other banksias, but known to be cultivated and is reported to be hardy (see references). It provides a nice architectural form with stiff leathery leaves.

Plant in a sunny spot and allow for drainage. Many banksias benefit from growing on a slight slope.

Do not mulch too heavily and try to keep grass away from the trunk. Very hardy once established. It is excellent for attracting honeyeater and other birds.

Will grow consistently if happy and will form a very nice shrub, to 3 m tall, but can be kept much more compact if pruned. May get sparse and leggy if not pruned. Very suitable for sandy and coastal gardens. Suitable for small gardens.

Do not apply a high phosphorus fertiliser as Proteaceae are generally sensitive.

Prune after flowering or harvest cut flowers. Likely not overly frost tolerant. Very tolerant to coastal salt spray.

Propagation

Other information

This species is very similar to Banksia paludosa and Banksia penicillata which also may also grow in the same habitat. B. penicillata is confined to cliffs and steep slopes in the Blue Mountains and so a location and habitat condition could be applied for identification.
B. paludosa has golden-brown to gold inflorescences and not the green-blue buds of this species. Reportedly, B. paludosa does not produce the new red-brown growth.

This species can regenerate after fire from the seed bank or from epicormic shoots and lignotuber after fire.

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 (Linneaus)).

oblongifolia – Latin referring to the oblong-shaped leaves.

Not considered to be at risk in the wild. Very common

http://anpsa.org.au/b-obl.html
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Banksia~oblongifolia
https://www.gardeningwithangus.com.au/banksia-oblongifolia-banksia/

By Dan Clarke