What is an old man banksia tree?
The old man banksia is a common woody tree species found along the east coast of Australia. The Darug word for banksia is wadanggari.
Old man banksias are named after their distinctive wrinkly grey bark. Their bark, gnarled and twisted shape and shiny dark green leaves with saw-toothed edges make them easy to identify.
During the flowering season in summer to early autumn, old man banksias feature cylindrical, pale yellow or cream coloured flower spikes. These spikes are large, ranging from nine to 12 centimetres wide and seven to 15 centimetres long. As these flowers age the flower spikes dry and turn a grey-brown. When pollinated, the flower spikes develop into large brown-grey woody seed pods called follicles.
The scientific name of the old man banksia is Banksia serrata. Banksia commemorates Sir Joseph Banks, the botanist who travelled with James Cook on his first Pacific voyage. Serrata is the Latin word for saw-edged, referring to the saw-toothed leaves of the old man banksia. Other names for the old man banksia are 'saw banksia' and 'saw-toothed banksia'.
Where are old man banksias found?
Old man banksias grow in well-drained sandy soils. They are often found near the coast, growing at the back of the sand dunes.
In Sydney, old man banksias are also found further inland growing in dry sandstone forests and woodlands.
How are old man banksia trees used by Aboriginal Peoples?
Fresh banksia flowers are nectar-rich and can be sucked or dipped in a coolamon of water to make a sweet drink. Smouldering banksia cones can be carried on a lined coolamon to transport fire between places.
What eats old man banksia trees?
The flowers of the old man banksia attract many native nectar-feeding bird species such as honeyeaters and wattlebirds.
Mammals such as flying foxes, possums and gliders have also been seen feeding on the flowers.
Yellow-tailed black cockatoos feed on the immature seed pods that form just after the flowering season.
What adaptations do old man banksia trees have?
Old man banksias are well adapted to dry conditions and poor soils. They have special roots that are efficient at absorbing the few nutrients that are available in the soil. Their leaves are hard and woody and do not require a lot of water to grow.
Their hard, woody leaves are also difficult for any herbivores to digest. Being an unappealing food source means that the old man banksia does not have to waste any nutrients or water on replacing eaten leaves.
Like other species of banksia, old man banksias are well adapted to fire. The thick woody trunk protects the interior from heat damage. After fire, leaves resprout from special ‘back up’ buds called epicormic buds found beneath the bark of the trunk.
The old man banksia is so well adapted to fire that its life cycle relies on it. The details of this are provided in the reproduction and life cycle section below.
How do old man banksia trees reproduce and what is their life cycle?
Old man banksias rely on pollinators for their reproduction. Native animals such as bees, birds and small mammals such as sugar gliders, pygmy possums and bush rats help transfer pollen between the flowers of different trees.
When the banksia flowers are pollinated they form woody seed pods called a follicle.
The follicles use fire as a cue to release their seeds. During a bushfire the seed follicles and open and the seeds are blown to the ground. The seeds germinate in ash-rich soil clear from other plants which would otherwise compete for sunlight and water.
Because of the relationship between fire and seed release it is important to prevent bushfires from becoming too frequent so that the new seedlings have an opportunity to grow into adults and produce seeds of their own.
In the absence of fire the follicles can also release seeds to the ground when they become very dry or when other parts of the tree are dying.
