Updated: May 17, 2021
There’s gold in them thar gum leaves …
yes, under specific circumstances.
But knowledge and data is also gold. It’s gold to researchers and we can help them find it. April 24 – 27 is the international City Nature Challenge and during this time people will be asked to collect data via photographs uploaded to iNaturalist. Images uploaded will be identified and collated.
In the Greater Adelaide region there are over 100 species of gum trees (as well as numerous hybrids and cultivars). Eucalypts or gum trees are drawn from three genera – Angophora, Corymbia and Eucalyptus (the largest of the three genera).
Eucalyptus and Corymbia have a bud cap, operculum, which is lacking in the flowers of the Angophora. The difference between Eucalyptus and Corymbia appears to be more subtle.Eucalypts Angophora Corymbia EucalyptusFlower cap Operculum No Yes YesAdult LeavesOpposite Alternate in most species* (opposite leaves in some species) Alternate in many species* (opposite leaves in some species)Corymb flower structure ^
^Image Jim Barrow
*As is the case with so many plant descriptions there will always be exceptions, but the chart above reflects the distinguishing features for the majority of the species in each genus.
Within each genus, other features will help to narrow down the identification. Features such as the type of bark, the tree shape, the leaf arrangement, the flowers and buds all help.
To ensure that we are able to identify to species level, it often necessary to take multiple photographs. This tends to be the case with our gum trees. The type of photographs to take are given in the following list
The whole tree
In some of the crowded forested areas, it may be difficult to see the whole of the tree but the habitat will be of help
The bark can vary considerably and is a useful identifier
If there are obvious different types of leaf, photograph them
Flowers or buds
As flowers/buds could be high up in the tree, check the leaf litter for them
It might be helpful to show the small flower stems
Gum nuts (Fruiting body), look for the fallen fruits in the leaf litter surrounding the tree.
Try and photograph that which looks typical
a cluttered background can make identification difficult
So get out there fossicking, you never know what nuggets you may find. Perhaps something rare.
Oh, and there is gold in the gum leaves in Kalgoorlie.
Examples of Photographs for Identification
A stand of young Eucalyptus camaldulensis along a creek line. Knowing where the trees are growing always helps; and though there were no flowers, the bud is clear and in focus, the background muted.
Examples of Poor Images
This group of photographs (above) of Corymbia citriodora is NOT a good set of images. Identification is difficult because of the cluttered photographs. An uncluttered, flat background will allow for clearer sharper images, making identification easier. In this instance it was not possible to get a clear picture of the whole tree but it would have been better to take the time, and place the leaves, bud and gum nuts on, for instance, a blank piece of paper or concrete paver and so obtain a better picture.
Thank you to Dean Nicolle for his assistance with this article.
Barrow Jim, Corymbia, Corymbia …. Wherefore art thou Corymbia http://anpsa.org.au/APOL19/sep00-3.html accessed April 12 2020
Eucalyptus, Corymbia and Angophora – Background
http://anpsa.org.au/eucal1a.html accessed April 12 2020
Discovering Gold in Gum Trees https://www.csiro.au/en/Research/MRF/Areas/Exploration-through-cover/Techniques-and-toolkits/Sampling-methods/Gold-in-gum-leaves accessed April 12 2020