Banksia plagiocarpa

A shrub, usually to about 5 metres tall.

It is restricted to Hinchinbrook Island in northern Queensland and the adjoining mainland close to the coast (between Townsville and Cairns). It was re-discovered after a long interval in the 1980s. On Hinchinbrook Island, it grows on the slopes of mountains in open woodland or grassland between 200 and 800 metres on rock or clay soils. However, on the mainland, it grows on lower altitudes on sand.

The leaves are alternate to whorled, somewhat stiff and leathery, elliptic to obovate, to 20 cm long and 1.5 cm wide with lobed to toothed to entire margins which are recurved. Dark green to blue-green on upper surface and white on under surface. New growth is covered in dense hairs and is red.

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 15 cm long and up to 6 cm wide, with each flower thin but up to 3 cm long, bluish-grey in bud, opening to pale yellow.

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 15 mm long with up to 60 follicles per cone.

The follicles have a strong wedge-shape.