Thursday, May 5, 2011

Kurrajong - The Perfect Shade Tree

Brachychiton populneus
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.


Stan Lusby said...

Thanks for the info. I witnessed Kurrajong in the drought of 1966. I had only been in the country for five weeks as a young immigrant surveyor and wondered then why they were not used in swathes as fire retardant protection for human settlements against the eucalypt killer fires like you have in NSW at the moment.

"Ignorance is not lack of knowledge but the mischievous desire to ignore."

Stan Lusby
Hsven Street
South Island NZ

Patricia Gardner said...

Hi Stan.
I am interested to hear your point of view. This is certainly a tree that performs well in the drought.
We do see Brachychitons used as minor firebreaks far more than you would have seen in here in 1966.
The problem with them is that they are not useful, in enough other ways, for it to be regarded as financially viable to sacrifice the amount of land that would be needed for firebreaks on a scale would have any effect on the kind of fire they're having in NSW at present. A hot fire in Eucalyptus country can jump many kilometres through the air to another stand of eucalypts. One would need great, long belts of kurrajongs many kilometres wide - not really a practical proposition.
A nice thought, though.

Anonymous said...

Hi Trish
I am planning to grow kurrajongs as an ember catch break around our house in the Adelaide Hills. Can the kurrajong tolerate frosts?
Thanks in advance.

Patricia Gardner said...

Hi Jules.
They are said to be able to tolerate frosts to at least -5°C.
do you know how cold your frosts are?
If you haven't already done it, next winter you might like to leave a maximum-minimum thermometer outside overnight in winter, in selected places (on a stake so it sits a few inches above the ground).
there are always quite wide variations in the temperatures around any given site, depending on the degree of slope and the amount of shelter. It is likely even to include some frost-free spots. Knowing your frosts can be a useful tool in choosing the right plants for the right places.
Of course another way of discovering whether a plant is likely to survive in your area is to find out if it grows naturally there. Choose a site with similar slope, aspect and degree of shelter, and Bob's your uncle!
Here's hooping Kurrajongs work for you!

margy.gill said...

We have a currajong in our front yard and love it. One problem is it drops a huge amount of sap which sometimes looks like rain and is very sticky. I assume it is because of the lack of rain. Is there anything we can do about it?

Patricia Gardner said...

Hi Margy.
Nice to hear from you.
I'm afraid I can't offer you any instant solution for the sap problem, which is not one I have come across, with kurrajongs.
Sticky sap is usually a sign of plant damage. Are you able to track down where it is coming from?
Is it an old tree?

Anne E said...

Hi, just had many ladies to my garden for a monthly garden club meeting. Many said the name of my unknown tree was a Kurrajong tree. However after reading and looking at google entries I'm not so sure. The tree has 3 prongs like the pictures, but it certainly doesn't tower. Do you think it could still be a Kurrajong?
Anne O'Brien

Patricia Gardner said...

Hi Anne,
Kurrajongs don't necessarily "tower". The street trees in Goondiwindi are quite small, despite apparently being old. The problem with tree height is that tree size varies with the soil and available water, but especially according to what is growing around them. They stretch tall if they need to compete with other trees for light, but stay low, broad and compact if they're getting plenty of sunshine. Kurrajongs (like bottle trees) are particular prone to this variability.
I find internet statements about the height of trees sometimes irritating. The writers seem to want to boast that they've found another even taller one, which was probably in a gully in a forest somewhere, stretching to match the canopy on the nearby hillside. The height may even have been a historic record, from the days when Australia had rather more in the way of forests and old trees.
The same plant in a garden might be a happy, healthy tree which reaches its maximum at a third or even a quarter of the claimed height. These extreme height descriptions do put people off planting them in their gardens, which is a pity. If we're growing a plant in a garden, we don't want to know the record height. We want to know what it's likely to do in a garden.
Better understandings of the likely height of garden plants come from plants which have grown in the open since they were tiny, such as those in streets, parks, and gardens.
The first photo in my article shows a huge tree in a garden in Millmerran. I have only ever seen another one of similar size that I could be reasonably sure was a planted specimen. (It is in the Helidon State School grounds) I suspect it would take 100 years or so to reach this kind of size.
The other characteristic which helps identify kurrajongs is the rather soft wood. As with bottle trees and flame trees, they sound a bit hollow if you knock on the trunk. It hardly even counts as timber, being the kind of thing cattle can eat. You wouldn't want children to climb any of these trees, as the branches would break fairly easily.
Hope this helps.

Robyn Bird said...

How long does it take a Kurrajong Tree to mature?
I'm really interested to plant more because I like the comment about them being fire resistant. i live on a bush block in a fire prone area.

Patricia Gardner said...

Hi Robyn.
The question is difficult to answer, as like so many "dry rainforest" type trees, kurrajongs are capable of being slow to the point of seeming to hibernate, or quite fast, depending on conditions.
For fast growth, they need to be kept moist in the root zone, (meaning the soil deeper than about 15 centimetres). The less water you waste on the surface, where most will be lost to evaporation, the better.
The soil moisture levels in much of the local region are perfect for planting right now, after the good rain. And to plant while the weather is still quite hot gives the little plants a reasonably long first growing season before winter sets in.
In drier times I have had excellent results from burying a large plastic bottle with a hole in the bottom beside each of my small trees, and filling them with water as often as possible for their first season. This wasn't with kurrajongs but with another dry rainforest species, but I think the effect would be much the same.
It's important to keep grass well away from all young trees, of course, and a layer of mulch both helps keep soil moisture in, and encourages healthy soil fungi which can make all the difference to young trees.
I think kurrajongs are a great choice for fire-prone areas. All species of dry rainforest-type trees are pretty good for this, too, so they're the sort of thing to look at if you want some variety.
Eucalypts and pine trees are the high fire risk plants, so are best avoided where fires might be a problem.

Anonymous said...

Hi Trish. I live in Mackay, Qld. I have two Poinciana's which unfortunately have to be removed due to root systems causing damage to the house so I am looking for a shade tree to replace them. Would the brachychiton populneus grow well here do uou think? And is the root systen invasive? Thanks, Toni

Patricia Gardner said...

Hi Toni.
I suspect kurrajongs wouldn't be very happy in your coastal climate. I can't remember seeing them when I was up there, and I think it would be too damp for them.
There are a lot of lovely shade trees native to your local area, which might suit your purposes better. I think you could probably get some good ideas and advice from the rather wonderful botanic garden you have there in Mackay.
There are also some very good books on tropical gardening. such as "Across the Top. Gardening with Australian plants in the tropics" by Keith Townsend, and others. You could try the shop at the botanic gardens, and maybe bookstores in town, for them.
Hope you find something wonderful to grow.

Tim Allen said...

Hi thanks for all this great info . I live on the coast the soil type is sand and ph level is 8.0 , do you think a
Kurrajong would be suitable ? . many thanks.

Patricia Gardner said...

Hi Tim,
The pH shouldn't be a problem, but the sandy soil might, and kurrajongs might also dislike the humidity of a coastal climate. This is a plant that likes its air dry.
There's nothing to stop you giving it a go, but it may be a long-term disappointment.
I am a person who loves to see plants growing in their own place in the world, where they participate actively in the web of life we call "the ecology". I would suggest that you think of exploring your local native flora for something else that might suit you better.
Australians are often surprised at just how rich their local plant diversity can be, once they start investigating. The result, should you choose this option, is a plant which loves to grow at your place. Robust good health always makes a plant more beautiful, and as a bonus, you get a plant that isn't an ecological "passenger".

Ed said...

I live in Tucson,AZ USA and the local nurseries here are selling these. I bought 10 of them that were already 5 years old. I've noticed on one of them that the leaves are a little wilty. I'm suspecting it's from lack of water. As soon as they were planted I watered them with drip emitters with 24 gallons of water each day for a week. Then I taperered off to every other day. 9 of them are doing great, but one of them is larger and showing wilty leaves. I'm watering that one every day still to see if that's the reason.

Patricia Gardner said...

Nice to hear from you, Ed
Are these plants in pots?
As you would have gathered from my blog, my experience is with growing them in their own native range, and of course we only grow them in the ground,where they flourish through our worst droughts. I have never seen them grown in pots.They have a large tuberous root, and I can't imagine that they would take very happily to long term pot culture. Deformed roots might make them prone to disease.
They would also hate to be overwatered, and could suffer from fungal diseases as a result.
However, it sounds as though yours are soldiering on despite their less than optimal conditions. Long may they continue!

Carolyn said...

My trees are planted with grass surrounding them. I am trying to water my grass and not over water the trees. The trees are losing leafs at a rapid rate and I think this is not good. Please help me!



Patricia Gardner said...

Hello Carolyn,
You don't say where in the world you are, so although you are writing in June I have no idea whether you are in early winter (southern hemisphere) or early summer (northern Hemisphere)
It is normal for kurrajongs to drop their leaves in early summer.
They don't do it every year, and sometimes the leaf-drop is only partial. Sometimes it is more complete. It usually means that the tree is going to flower (something they also don't do every year). If the flowers are pollinated, they will then produce seeds, which you can grow, to make more trees. If you do this, check the roots as they grow to make sure they have enough room in the pot. Kurrajong seedlings have a large tap-root like a fat carrot, and need plenty of room for it.
You can also eat the seeds (lightly roasted) or make a coffee-like drink with them, but make sure that you rub the seeds well (with gloves on) to get rid of their hairy little coats. Those little hairs are prickly and will leave tiny prickles in your mouth!
Don't worry that you might be over-watering the ground your tree, unless your soil is rather soggy or swampy. Kurrajongs are very tolerant, and happy to be given some water if the soil drains well, especially when they are making new leaf after a leaf-drop.
Let me know how it goes after a few months.

Finn Englund said...

Interesting posts here! My question is about getting potted plants to survive. I picked some seeds from pods on the ground 2½ years ago in Morocco and successfully planted them back home in Stockholm, Sweden. Only today did I get them clearly identified as Brachychiton populneus. I am grateful for this explanation of the remarkable difference in leaf shape juvenile/mature. Now: I will keep them as indoor plants, obviously, for as long as they want to cooperate, but I have to cut them down before they hit the ceiling. And the stems are so thin! Can they be cut radically? Will they survive? Will they branch out?

Patricia Gardner said...

Hello Finn.
Good to hear from you!
I am astonished at where these plants turn up! Morocco and Sweden!
As you would have understood, my blog is really intended for people in my part of Australia, who are interested in growing their own locally native plants. I have never heard of Kurrajong being grown as indoor plants. I am not surprised that they are long and thin. I am probably not as surprised as your little kurrajongs, though, which must be astonished to find themselves growing indoors in Sweden! Such a very different place from their native country.
This is not a tree that anyone usually wants to cut at all, but I have seen them pruned near Dubbo. They were being cut to feed their leaves to Giraffes at the zoo. They seemed to like it well enough, and grew into a trees with dense rounded canopies.
I would suggest you give them a try.You have nothing to lose!
Best of luck with them.

Barb said...

Hello Finn, I have a small, self seeded, Kurrajong which is growing 10 feet away from my house. I am encouraging it to grow as it will provide lovely shade for our porch which faces north west. My husband is worried about the roots? I have always thought Kurrajongs had a large tap-root, so I thought would be ok planted near paths and the porch? Is this wishful thinking on my part?
We average about 12 inches of rain per year and I water my garden regularly. Many of our street trees are Kurrajongs but a lot of people here curse them because they can be messy. I love them. Can you tell me if I will have a problem with the roots?
Thanks in advance,

Patricia Gardner said...

Hello Barb.
Sorry for the slow reply. No comments are published on this site until I (as the owner of the blog) have had a look at them and decided whether to publish them. It keeps away the peculiar people, and those who want to use my comment section for advertising etc.
People who badly want an answer to a question tend to email me at the contact address given, rather than to ask through a comment.It does get a quicker response than waiting for me to look up my "comments awaiting moderation".
Because this is a personal blog, rather than a forum, it is not a particularly suitable way to have a conversation with another comment writer, either. Finn is very welcome to reply, of course, if he happens to read your comment.
With regard to your query, you will notice that I have advised in the body of the blog that kurrajongs should not be planted closer than 3.5 metres from water pipes or sewage lines. Because these items carry water, they are more prone to attack by the roots of living trees than are house foundations or paths.
I may have been being overcautious when recommending 3.5 metres. Brachychitons generally have a bad reputation in this regard, but they are not all the same, of course. Kurrajongs, being a dry-country cousin of most of the other Brachychitons, are likely to have deeper, less spreading roots. I notice that the Western Water site (a peri-Melbourne water authority) considers kurrajongs acceptable within 2 metres of sewer lines (and that they are the only brachychitons it recommends for planting that close).
So at 10 feet away, you can probably be confident that your kurrajong won't pose a threat to your porch foundations.
You might like to confirm this, for your husband's peace of mind, by doing an internet search on "sewer pipes" and "kurrajong".
Trish Gardner

Barb said...

Hi Patricia,thanks for your reply. I must explain, I wrote to you twice because I was sure I lost this first post. I must have been having a bad day. I also apologize for getting names mixed up. I realize now, I used Finn's name instead of yours. Silly old me!
Thanks so much for your advise regarding my little Kurrajong. We have just had some wonderful summer rain and more little leaves are appearing. Thanks again, much appreciated.
Barb :)

Patricia Gardner said...

Hello again Barb.
Having taken my own advice, and looked up what various regional water authorities and local councils recommend in the way of planting distance away from sewer pipes, I began to wonder whether I had given good advice at all in suggesting that you do an internet search! I was astounded at the lack of consistency between the recommendations. One site (Western Water, a water authority near Melbourne) thinks that a kurrajong (Brachychiton populneus) can be safely planted 2m from a sewer line. Another recommends you keep it more than 6 metres away, and yet another recommends more than 10 metres. Presumably the writers all claim to be experts, or they wouldn't be writing things like that for local governments and water authorities, but you really have to wonder how much some of them really know!
After a bit more trawling, I began to wonder whether whether some of the people who compiled the lists even knew what the plants on their lists were, let alone what their root systems are like. Their distance groupings were such an odd hotch-potch. The same distance recommendations are made for plants on a list that includes of water-hungry species that should obviously be kept away from pipes, trees with a broad, shallow root-reach that would interfere with foundations and footpaths, and small-rooted drought hardy things that are hardly likely to be a problem at all. I got the impression that some of these people would prefer to have no plants in our suburbs at all. Our pipes would be VERY safe, but would be be having any fun?!
One of the sites that impressed me as having been written by someone who knew what he/she was talking about was
It didn't refer to kurrajongs,though. The only Brachychiton it mentions is Brachychiton acerifolius (Flame tree). They recommend keeping it 4 metres from sewer pipes. Flame trees are less drought hardy, and have higher water needs than kurrajongs (Brachychiton populneus, and by inference you could plant the latter closer than 4 metres to a sewer pipe, and closer still to foundations.
The final decision is yours and your husband's, though.

Patricia Gardner said...

Hi Barb.
A lot of people write double comments. There is something horrible about having taken the trouble to write, and have it disappear into the blue, isn't it. I have explained the process in the fine print somewhere, but it's easy to overlook.
As you will see, your comment gave me a great deal to think about, and I posted another blog on the subject of tree roots and built structures, and mentioned your query. More reliable information is definitely needed.
It will be interesting to see whether it pulls out any responses.