Yardalbara or the Ooldea mallee, Eucalyptus youngiana, is one of the Great Victoria Desert's most spectacular plants. In winter or spring, its magnificent flowers and fruits make a trip to the South Australian section of the GVD a memorable experience. Eucalypt expert Dean Nicolle assures us that the fruits are heavier than those of any other eucalypt. The Western Australian rose of the west, Eucalyptus macrocarpa, has slightly wider fruits and flowers but they are lighter and this tree does not range into South Australia. This makes identification very easy – if there are no flowers, look on the ground under the tree for the massive woody fruits which can be up to 70mm across. If you're on the South Australian side of the border, the tree is the Yardalbara.
Like so many desert and arid area eucalypts, this tree survives with the help of a lignotuber, a large woody swelling which stores carbohydrates and water. The lignotuber is usually underground to minimise water loss. Following bushfires and storms, new trunks grow from the lignotuber's 'adventitious buds', the eucalypt's equivalent of a potato tuber's eyes. A single lignotuber may have up to 13,000 buds, though only five to fifteen normally become trunks at one time. Aboriginal people would cut lignotuber sections from mallee eucalypts, seal them with clay and carry them as water sources.
Eucalyptus youngiana takes its English common name from Ooldea, the now-abandoned settlement on the transcontinental railway line where Daisy Bates lived with the local Aboriginal people for many years in the early 1900s. Yardalbara is the local Aboriginal name for the tree. The scientific name honours Jess Young who collected the original 'type specimen'. Young was a member of Ernest Giles' east to west expedition in 1875.
On first seeing this superb tree, a Friend of the GVD was moved to poetry:
In spring 1875,
When the style was all Victoriana,
A bloke known as Jess Young (not Clive)
Found Eucalyptus youngiana
He gasped when he noticed the flowers
And the simply splendiferous fruits.
He sat there and watched them for hours,
Then cut off some specimen shoots.
This tree is a mighty survivor –
After fire it will beggar belief.
It's soon clothed, unlike Lady Godiva –
New stems put out leaf after leaf.
Forget trees from places exotic –
Step forward and sound the reveille!
You're Australian, so be patriotic –
Start planting the Ooldea mallee.
The Red Form. Yardalbara flowers have three colour forms – red, pink and yellow.
The Pink Form. Like all Eucalyptus flowers, Yardalbara has many showy stamens. These are the male parts which produce the pollen.
The Yellow Form. The stamens surround a central style – the female part which produces the seeds when pollinated.
Typical Yardalbara Habitat. As you walk among the red sand dunes, the Ooldea mallee at first looks like any other mallee tree – straggling and multi-trunked. However, the large fruit (gumnuts) will usually be found on the ground under older specimens. They can clearly be seen in this photo.
"A Mighty Survivor" All the above-ground parts of this tree were killed by fire. The dead branches remain. Below them, new branches are shooting up from the lignotuber as explained above.
Flower Buds. "Eucalyptus" comes from the Greek for "well-covered" and all Eucalyptus species protect their developing flowers with a cap, properly called the "operculum". The caps help to distinguish the hundreds of species. Eucalyptus youngiana has a big flower, so it needs a big cap.
Goodbye Operculum. The operculum is forced off the gumnut as the flower grows to its full size. This one is being helped off by a bloke with dirty fingernails.
The Gumnut. When flowering is over, the stamens fall off and a woody fruit develops. Australians call all Eucalyptus fruits "gumnuts".
New Flowers and Old Fruit. This is a new flower at its peak, backed by the red developing fruits from slightly older flowers. The stamens have dropped off these fruits, but the styles persist.