EUCALYPTUS TREES ARE EVERYWHERE
This painting of glorious gum trees was inspired by a walk along the banks of the Little Para River in Adelaide’s northern suburbs.
You’d be hard pressed to go more than 10 minutes without spotting a eucalyptus tree in Australia.
They dominate our landscapes from the bush to our backyards, paddocks, parks and pavements.
And they even have their own national day — on March 23.
Eucalypts form about three quarters of the tree flora of Australia.
Eucalypts are widely distributed over the Australian continent. They range from the dwarfed and stunted forms called ‘mallees’ to the tall trees which grow in coastal and mountainous regions.
Eucalypts are typically native to Australia although a small number of species have been found in neighbouring countries. Contrary to popular belief the extensive plantations in North and South America, Europe, Africa, China and India are not native but were all grown with seeds from Australia.
HISTORY OF EUCALYPTUS TREES
The eucalypt belongs to the Myrtaceae family. The genus was named Eucalyptus by the Frenchman L’Heretier in 1788. The word came from the Greek eu ‘well’ and kalypto ‘I cover’ and refers to the cap that covers the flower buds until the buds mature and force the cap open.
The roots of the eucalypt go back to when Australia was part of the supercontinent Gondwana.
The oldest known examples of eucalypt fossils are 52 million-year-old flowers, fruits and leaves found in Patagonia.
Sequencing of the eucalypt genome from the rose gum (Eucalypt grandis) — a species found in coastal areas of New South Wales and Queensland — indicates the group goes back at least 109 million years.
At that time, flowering trees were starting to take off and dinosaurs roamed the land.
A diverse Australasian
Today, botanists have identified around 900 species of eucalypts divided into three different groups: Eucalyptus, which make up the bulk of the species; Corymbia, the bloodwood eucalypts mainly found in the north; and Angophora.
Eucalypts come in all shapes and sizes and dominate the landscape from alpine regions to the outback and edges of rainforests.
There’s the mighty mountain ash (Eucalyptus regnans), the world’s tallest flowering tree; the gnarly snow gum (Eucalyptus pauciflora); the multi-stemmed bull mallee (Eucalyptus behriana); the apple or cabbage ghost gum (Corymbia flavescens) found in northern Australia; and the twisted Sydney red gum (Angophora costata).
The only place they don’t really dominate is the very, very arid parts of Australia.
One of the most distinctive features of eucalypts is their bark.
Some trees have smooth bark — as the tree grows it sheds old layers from its trunk or branches. The new bark underneath is often brightly coloured that fades over time.
There are also half-barked trees that have thick bark around their trunk but smooth limbs.
Other trees are completely covered in rough bark. The old layer of bark stays attached to the tree and forms a thick protective layer against fire. Rough barks can be a bit trickier to identify because the texture can take different forms.
If the bark has long stringy bark, it might a stringybark, if it has tough, blackened furrowed bark it might be an ironbark, and if it has really short fibres it might be a box or a peppermint.
There are about 30 species in eastern Australia that can be classified as stringybarks, but the word gets used for similar species that are not closely related.
The Darwin stringybark (Eucalyptus tetradonta) used in Aboriginal bark paintings in the Northern Territory is one of these false stringybarks.
Indigenous people across Australia also use bark to make canoes and shields.
In New South Wales, Victoria and Queensland there are a number of protected scarred trees. As the name suggests these trees bear scars from where the bark was cut away and sometimes engraved.
A eucalypt’s leaves are packed with oil glands that produce the aromatic compounds that give us their distinctive scent.
Some smell very strongly eucalyptus-like, some smell really like peppermints, and the lemon-scented gum has a more lemony smell.
These compounds help protect the tree from attack by pests.
Oil glands make them unpalatable to insects, but then you get insects that adapt to eating those sorts of leaves.
Gumnuts are actually hard, woody capsules have a thick wall, which is not destroyed by heat. The capsules open up after fire to release the undamaged seeds.
FIRE RISK OF EUCALYPTUS TREES
Features such as oil-filled leaves and bark that can easily shed make eucalypts highly flammable.
This ability to stoke a fire is part of their survival strategy.
If a fire is hot but goes through fast it will do less damage than a really slow burning fire.
The fact that that helps fire go through fast was clearly a selective advantage to the species because then their seeds wouldn’t have been cooked.
Even if the tops of the trees are destroyed by fire, many species can re-sprout from buds under their bark or from a lignotuber at the base of the tree. But not all species can re-sprout.
Why are eucalyptus trees called ‘gums?’
In 1688 William Dampier noted that trees in north west Australia exuded a type of gum.
Aborigines used this gum to fasten barbs to the ends of spears and fishing sticks and to treat cuts and wounds.
The exudation from the bark which looks like a ‘gum’ is actually a tannin-like substance known as ‘kino’. Governor Arthur Philip is credited with being the first to call the eucalypt a ‘gum tree’ in 1788. Since then most Australians have called eucalypts ‘gum trees’.
The characteristic fresh fragrance of Australian eucalypt forests comes from the leaves releasing some of their eucalyptus oil.
All eucalypts have eucalyptus oil in their leaves. The quantity and type of eucalyptus oil varies from species to species.
USES OF EUCALYPTUS OIL AND LEAVES
Researchers examined the psychology of food cravings and found the use of counter-visualisation – in particular, imagining the scent of Eucalyptus Oil – was highly effective in curbing cravings.
Koalas and other animals eat from the eucalyptus plant in the wild.
Health benefits and uses of eucalyptus oil and leaves –
- Eucalyptus leaves and essential oil have antimicrobial properties
- Sinus Decongestant – add a few drops of the oil to hot water and inhale the steam.
- Infections, fever, upset stomach, and to help loosen coughs.
- Immune Stimulant
- Sore Throat Spray
- Joint & Muscle Pain Reliever
- Disinfecting Cleanser
- Dental Anti-microbial
- Fungal infections and wounds
- Insect repellent
- Asthma Relief