Fern leaf banksia

Fern leaf banksia

Banksias are generally associated with coastal heath. Different species are, however, found from the coast to montane regions. The fern leaf banksia (Banksia oblongifolia) is found along the east coast of Australia from Woolongong to Rockhampton growing in sandy heath soils, swamp margins and as an understory in eucalypt forests. In the former regions, in very low nutrient soils it only reaches a height of about a metre but in richer, forest soils it can grow to 3 metres in height.

This shrub has several stems growing out of a woody base (lignotuber) that has dormant buds and contains food reserves. New leaves and branchlets are covered in a rusty fur that is shed as they mature. The adult leaves are green above and whitish underneath, arranged alternately along the stem, about 10 cm long and are oblong or egg-shaped. The margins are mildly serrated. Between January and October flower spikes arise from the ends of the branchlets. These 15 cm long cylindrical spikes are composed of a large number of flowers that start as blue-grey or greenish yellow buds that open to yellow. They produce copious nectar which is used as a bush food, or medicine for coughs and colds, and which attracts a large variety of honeyeaters and bees. It is also a butterfly host plant. The spikes lose their flowers with age and become swollen and woody. Each flower’s ovary is embedded in the spike, and develops into a seed pod or follicle containing two seeds.

Banksia oblongifolia can live for over 60 years, in spite of the fact that they live in areas prone to bushfire. They have two fire survival strategies. After fire, the dormant buds on the lignotuber sprout and two to three years later they can flower and set seed. The heat from the fire causes seeds to be released from their follicles and thus a new generation of plants become established. Banksias have evolved in Australia’s phosphate-deficient soils and have specialised roots that form dense mats of short lateral rootlets just below the leaf litter. These enhance nutrient uptake by increasing nutrient solubility.

Being adaptable to different well drained soil types, these hardy, slow-growing shrubs are ideal for small, sunny or lightly shaded gardens. They are low maintenance plants that can be kept in shape by pruning to form, for example, a colourful border. They grow well in containers and are amenable to bonsai. The flowers and fruit are a useful addition to floral arrangements.

Banksia oblongifolia
Banksia oblongifolia. Photograph by Heather Knowles.
Banksia oblongifolia
Banksia oblongifolia. Photograph by Heather Knowles.

 

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