The Rainbow Tree
Imagine going on a backpacking holiday in South East Asia. You’ve just met a group of fellow travellers at your hostel, and you’ve all decided to go on an early morning hike through the dense rainforest.
The hike has been going on for hours and its starting to get very warm; a few friends are already complaining at the back. You keep walking, pass under a few overhanging giant leaves and hear a few strange animal noises. Then, you see a familiar tree. It looks like a Eucalyptus from back home in Australia. But as you approach it, you notice something is not right.
The tree bark is multicoloured- its bright green in some areas, fuchsia in others. There is also blue, red, orange– all the colours of a rainbow!
‘’This can’t be real, maybe someone painted it,’’ says one of your friends. You all stare at it and try to comprehend what you are seeing.
‘’…I think we’ve been drugged.’’
Eucalyptus deglupta bark, JM Guay (Fickr)
Rainbow Gum – a very special tree
The group of friends in the story above have encountered the Rainbow Gum, Eucalyptus deglupta. This tree belongs to the Myrtle family and is native to the Philippines, Papua New Guinea and Indonesia. It is one of the handful of Eucalyptus species that is not native to Australia. It has adapted in different ways to the tropical environment it lives in. For example, the leaves of the rainbow gum do not produce as much oil as most Australian species. This is because there are not as many bushfires in South East Asia.
Why is the tree so colourful?
The rainbow gum peals its skin off, revealing different colours beneath each layer. It starts off as bright green, and then changes to dark green, blue, purple, pink and finally orange. The pealing occurs in different parts of the tree at different times, which gives a unique pattern to the bark. Some people refer to this tree as a ‘living art-work’ because of its everchanging physical appearance.
The exact science behind this phenomenon is still unknown. But over the years theories arose, and the most popular was proposed by the Professor David Lee from the Florida International University. He believes that the colouring of the layers is due to a combination of chlorophyll – a green photosynthetic pigment found within cells– and tannins – an organic brownish substance found in some foods and plants.
He believes that the outermost layers of the bark are filled with tannins which interact with the levels of chlorophyll in the other layers. As the tree shed more outermost-bark, the inner layers which contain less tannins are exposed. There are also different amounts of chlorophyll in the different layers, and all these different combinations of substance levels give off different colours of the spectrum. We are also able to see this because the layers of bark are covered by a cell layer that is transparent.
Can I grow one at home?
Now that you’ve read about this awesome tree, you might be wondering if you could ever have one in your backyard. The answer is yes, this tree can grow in other non-native environments. However there is a catch because the colours will be less vibrant…