Euc Beaut! A tribute to an Aussie Icon

The National Herbarium of NSW has a collection of eucalypts (Eucalyptus, Angophora and Corymbia) that would fit comfortably under the shade of one decent sized gum tree. It contains 73,664 specimens, samples of the genetic variation of the eucalypts through time and space.   Through botanists like Joseph Maiden, Lawrie Johnson and Ken Hill the collection has been at the forefront of Eucalypt taxonomy for 120 years. This collection helps to describe many species and our understanding of the relationships between those species.  More recently, we have targeted numerous eucalypt species as part of our Restore and Renew project and call on citizen scientists to help us map natural tree hollows for Hollows as Homes. Here are a few reasons why we love eucalypts. 

They provide a safe habitat

There are around 300 species in Australia that are reliant on tree hollows for shelter, nests or a temporary resting spot along their journey. Mammals, birds, reptiles, insects and frogs seek out hollows and are particularly fond of eucalypts. Hollow creation is a slow process, especially in Australia where we rely on fungus to eat away at trees rather than an efficient wood pecker. Eucalypts have a long life span allowing more than enough opportunity for a fungi feast helping to create homes for our wildlife. 

They are resilient  

Eucalypts have evolved to live in dry environments with long dry spells and have many adaptations to withstand fire such as:

• insulated seeds which open only in response to fire
• oils in the leaves help fuel a fire thus making it more intense and detrimental to less fire-adapted species and giving an advantage to eucalypts
• ‘epicormic buds’ under thick bark are ready to sprout new stems and leaves after a fire
• because eucalypts have leaves low in protein and high in toxins they are predated on by few species except the Koala and eucalyptus leaf beetles like the Chrysomelidae.

The diverse flower and fruit

There are over 700 species of eucalypt and their diversity is reflected in the shapes and sizes of their fruits – from large gumnuts of mottlecah, Eucalyptus macrocarpa a Western Australian mallee gum to the tiny capsules of forest giants on the east coast such as the mountain ash, Eucaltyptus regnans.   The brush-like flowers of most Eucalyptus allow open rewards for a wide diversity of animal pollinators, such as insects, birds and mammals. Some Australian species such as E. forrestiana appear to focus exclusively on bird pollinators. Their bizarre long, red, and pendulous flowers make it difficult for insects to access nectar, saving the reward for birds.

Our Science team put together their favourite facts about eucalypts, see how many you know and select a few for your next trivia night.

• The name Eucalyptus was coined by a French botanist in 1788 by the name of Charles Louis L’heritier de Brutelle (1746-1800). Its name is derived from the Greek meaning ‘Well covered’ and refers to the unique covering of the flower bud.
• Arguably the most favoured eucalypt for consumption by koalas is actually a hybrid between the swamp mahogany (Eucalyptus robusta) and the forest red gum (Eucalyptus tereticornis).
• The strawberry gum, Eucalyptus olida, has a strong fruity scent and is often used in herbal teas and other bushfoods.
• Eucalyptus lehmannii is strange among the eucalypts as it has large, green flowers and forms compound fruits.
• Eucalyptus macrocarpa from Western Australia has the largest gumnut of any Eucalyptus species. They can measure nearly 10 cm across.
• The genus contains the tallest flowering plant alongside some plants of very small stature.
• The biggest tree in NSW is a Eucalyptus grandis near Bulahdelah.
• Some eucalypts are very plastic and they can occur across a range of habitats and look completely different in different environments. For example, Eucalyptus pauciflora, which is very variable and has tree and mallee forms.
• Eucalypts can be small – Eucalyptus cunninghamii is a mallee that usually grows less than 1 metre tall. From a distance it does not look like a eucalypt, but looks like a shrub.

We aren’t the only ones who love eucalypts

• May Gibbs used bush plants like the eucalypts for her children’s books ‘The Complete Adventures of Snugglepot & Cuddlepie’, and which was also a theme for 2018's Vivid Sydney. 
• Soldiers returning by ship from the world wars are said to have been able to smell the aroma of the eucalypts before land was visible on the horizon.
• Eucalypts love themselves and are very promiscuous. Not only do they hybridise, but there are cases of hybrids between more than two species. There are a number of records of hybrids or intergrades between three species in the National Herbarium of NSW.

It doesn’t stop there, the eucalypt plantation all over the world totals to well over 20 million hectares:

• India ­ over 3.9 million hectares (22% of world acreage)
• Brazil – over 3.7 million hectares (20%)
• China – over 2.6 million hectares (14%)
• Australia (by contrast only 5%)

So to wrap up our love for the ol’ gum tree we leave you with our favourite fact:   The oldest eucalyptus fossils come from Patagonia (Laguna del Hunco – 52.2 mya). Steep, unstable Andean slopes on volcanic ash were their likely preferred habitat.

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