Kurrajong - The Perfect Shade Tree

Brachychiton populneus
Family: STERCULIACEAE
Kurrajongs are dry rainforest trees which take the “dry” more literally than most. We see them far out on the western plans, as in this specimen in a Western Downs town which is doing such a good job of shading a cool Queensland-style house.

Their deep roots help them survive droughts. Deep roots also mean (as with other dry rainforest trees) they are less likely to create problems for buildings and other structures. However the roots do seek water, so should not be planted closer than 3.5m to water pipes or sewage lines.


Another part of the secret of kurrajongs’ drought survival is the capacity to drop their leaves in dry winters. The degree of leaf drop depends heavily on the availability of soil moisture, so in wet winters they may lose very few of them. This photo was taken near Toowoomba in June 2008, which was probably the driest of all the dry times in our recent long drought.




The species can grow tall, as shown in this bushland example, also near Toowoomba. Usually, rainforest species only grow this shape if surrounded by other trees. It is possible that this very old tree spent its youth in a quite different environment from the grassy eucalypt woodland you can see in this modern photo. A great deal of such country, along the Great Dividing Range and the valleys to the west of it, was once dry rainforest. It was cleared so long ago that we have forgotten it was ever there. The shape of this tree may indicate that this was the case here.


Kurrajongs have a very pretty flower, and unlike some of the other Brachychiton species (notably the flame tree Brachychiton acerifolius), they don’t link flowering with leaflessness.
This photo was taken in October, and the tree had a shady green canopy.
While mature trees can put out a great show of flowers, it won’t happen every year, so the kurrajong’s ornamental qualities are largely based on its cool green canopy.


As with many Australian trees, their juvenile leaves differ from the leaves on older trees. These leaves are from a very young tree.









The shape on the right is the one we most commonly see, while the one on the left only occurs on mature trees.








I photographed this paddock of kurrajongs at Gilgandra. They were neatly pruned, and I wondered why. Then we drove on to visit the Dubbo Western Plains Zoo, where we watched giraffes being fed with kurrajong leaves. No doubt this explained the mystery!

The photo is such a good demonstration of the results that we can get from pruning most of our dry rainforest tree species. You can see how well these Australian native trees would grace a formal garden. They can be kept to a size suitable for the suburbs, and make very good street trees, as seen in Goondiwindi.




This young kurrajong in Crows Nest is being groomed for the job.









Pastoralists have long recognised the value of kurrajong leaves as emergency drought fodder for their stock. Unfortunately they have all too often solved their problem by cutting down whole trees, a curiously short-sighted solution. The result is that, while we see many young trees in the Toowoomba district, large, old ones are rare.


Kurrajongs are host trees for one of our larger butterflies, the tailed emperor (Polyura pyrrhus sempronius). We caught this delightful pair “kissing” in the bushes at Kwiambul National Park last weekend. (Butterflies kiss with their antennae.)


Brachychitons are recognised as being fire resistant. A row of them on a fenceline downhill from the house, in bushfire-prone areas, could make all the difference (though of course no tree will resist a very large bushfire). A green canopy catches sparks, and might just be the factor that saves a house from catching alight.
A “home among the kurrajongs” is a very Australian image, and considerably safer than the one among the gum trees which is celebrated in the well-known song.
Kurrajongs can be transplanted at up to 8 years old.

PROPAGATING KURRAJONGS
I have done quite a bit of this, and regard it as a pig of a job.If you are going to handle the seeds, you need to wear gloves because of the tiny irritating prickles on the seed coats.
So I was delighted to receive the following suggestions from a reader, Rob, from Canowindra:
I have just started to grow more from seed as we have had rain. My method is to scrape the seeds from the pods, when ripe, with a screwdriver. Place seeds in a capped jar with a couple of pebbles and shake vigorously to remove husks. Flushing the jar with water will remove husks and then just dry the seed in the sun for storage. To germinate, I put mine in a jar and pour RAPIDLY boiling water over them. I then place them in a folded, moistened kitchen paper and place in a zip lock sandwich bag. Last group was ten seeds and all germinated. Presto, in a couple of days roots appear and they are ready to pot. Keep the water up to seedlings in our area and the growth is phenomenal. I’m sure God smiled when he gave us Kurrajongs! "
Thank you Rob. I have only used hot water from the tap. We do have a very hot solar hot water system, but I am interested to hear how well your seeds respond to the boiling water.
I feel sure this method would also work for bottle trees. I would be a bit more cautious about the very hot water for Brachychitons that come from scrub or rainforest habitats where fire is not part of the ecology.
Rob also says that Kurrajongs are recommended as a suitable species for Bonsai, so if you have no room in your garden, you could grow some for this purpose, or just as attractive pot plants.