Cadagi Tree

greg1958October 10, 2006

The Cadagi Tree (Corymbia torreliana)

This rainforest tree from North Queensland was used extensively in the 70Âs and 80Âs as a fast growing attractive shade tree in South East Queensland. It has an attractive shape and broad fury leaves. New leaves commence as red tips which make it pleasant to look at. The large flowers open in November, and appear to be well visited by the Native Bees. It is a valuable tree as far as food is concerned.

The Cadagi is one of these trees that causes a problem in the environment. Many councils along the east coast of Australia have listed the species as an undesirable noxious weed.

Although they are a very fast growing shade tree, probably the hardiest in your paddock and it was one of the most extensively planted shade trees in South East Queensland they are creating havoc for our native stingless bees.

Humans weren't the only forms of wildlife to go crazy for these trees. Our native bees also found them irresistible and this is where the problem lies.

To Bee or not to Bee

After pollination, the seedpods of the Cadagi develop and begin to open in early January and continue to mature until the end of February. This is a serious period of time for native bees. The bees collect the resin that spills from the seeds and mix it with their own native bee wax to be used as nest building and sealing material.

The bees become obsessed with the collection of resin but the problem lies with the resin being attached to the seed, translating to thousands of seeds being carried home by the bees. The determined little bee can be seen carrying two seeds home on their back legs which is an extraordinary feat considering each seed is approximately 1½ millimeters in diameter.

So with this process we have created 3 major problems.

Firstly a Clogged Front Door

There are literally thousands of seeds carried home. The inside for the box is lined with multiple layers of seeds. At the entrance of the nest, there are so many seeds, that the entrance may become completely clogged. A clogged up entrance may prevent air movement and cause overheating, and possible death of the nest. Obviously the bees cannot get in or out either.

Overheating and Collapse

The multiple layers of seed continue to exude resin that is in such large quantities that the fumes on a hot day may kill the colony.

Obsession with Seeds

From observation, the bees will continue to collect excessive seeds and resin during this traumatic period. Unfortunately they forget to clean up or guard the hive leaving it susceptible to one of its great enemies, the native fly.

And just in case any of us are left wondering how this 'natural' event could occur. The native bees and the Cadagi do not naturally occur together. We have brought the tree to the bees.

If that isn't enough to convince any would be planters keep in mind that the Cadagi is also a pest hosting tree which attracts Monolepta beetles and beware of parking your vehicle under...

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Wooroonooran(NE, NSW.)

too true, I have also heard that this species is known to hybridise with E. saligna. I have either poisoned or had all Cadagi's trees removed (about 15 all up).

I lived in far northeastern nsw for over 20 years and in tropical queensland for the remaining 7 of my life. This is a fortunate situation as I can compare the many similarities and differences between the Wet Tropics and the southern border ranges- Sunshine Coast rainforests. As C. torelliana can be found in both locations I guess I have found this interesting.

Some questions I would like to ask you is.
You say 'the native bees and the trees dont occur together'
What are the natives bees? I think this because we have native Trigona bees in north queensland which are known to visit Cadagi trees. Why dont they go extinct? The bees obviously survive in the natural habitat of C. torelliana. The Trigona genus is extant within both locations NENSW/SEQLD and additionally in the Wet tropics.

Regards from Kris

    Bookmark   October 11, 2006 at 8:42AM
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gardenlen(s/e qld aust)

yes a typical exapmle of a native from one are being the worst weed in another and yes detrimental to native bees. and they are growing wild in all bush areas.

everytime i drive around brisbane i see heaps of them and wonder why common sense doesn't prevail and remove these trees. i don't visit nurseries but that is the first place that should stop selling these plants.

the safest tree is an indemic native to that specific area.


Here is a link that might be useful: lens garden page

    Bookmark   October 11, 2006 at 3:26PM
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For something from a high rainfall area, its ability to come up and grow in drought conditions near Rockhampton is interesting. Fortunately they respond nicely to common medicine. Long after they were recognised as a problem, I was astonished to overhear a nurseryman in Rocky still promoting their use.

    Bookmark   October 11, 2006 at 6:18PM
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Wooroonooran(NE, NSW.)

just a quick comment.
You mentioned..
'the safest tree is an indemic native to that specific area'.

This is true but Id almost go as far as saying 'no one does this'.
To do the right thing, everyone must plant only what occurs/ed in the Regional Ecosystem/s that occur/s on their property, otherwise they are introducing a plant to a new location where it shouldnt be.

Regards from Kris

    Bookmark   October 11, 2006 at 11:11PM
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gardenlen(s/e qld aust)

yes kris,

not many do, do it hey?

there are a number of us now who are seeinmg that this error of our ways stuff should be taken on board a bit more by sensible gardening techniques.

outside of food trees and with our current lack of rainfall in the country, more and more indemic natives should be planted, and that need not mean a boring uninteresting garden.

i don't frequent nurseries much at all nowadays, but from what i have seen they still flog off plants that are known weeds, and i'm sue if i looked they will still be selling the cadagi gum, along with the queen palm, and for s/e qld the alexander another from the wet north taking over silently and cross pollinating our native bangalow.

the list goes on agave's, broms, crucifix orchids lots of succulants mother of millions still and always will be a major problem with no known controls & lantanas.


Here is a link that might be useful: lens garden page

    Bookmark   October 12, 2006 at 2:09PM
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artiew(QLD Aust)

One of the first things I had done when I bought my current house in Rocky was to have the large Cadagi at the front completely removed. Used the woodchip as mulch, and most of that has now disintegrated, so the tree did serve some purpose in the end. Astounding how many poor planting choices we see on a daily basis, but I'm preaching to the front row of the choir on this one.



    Bookmark   October 13, 2006 at 1:55AM
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trish_g(SE Qld Aust)

I have heard a story that the Forestry Dept (or whatever it's called these days) is growing Cadarghi x spotted gum. Does anyone know about these? Has research been done, I wonder, on the effect of these hybrids on on native bees? Meanwhile the ordinary E. torrellianas are still being sold in nurseries and on SGAP stalls, and are spreading in the wild - their seeds being carried about by introduced honeybees, which take the seeds home, but sensibly drop them outside their hives after removing their waxy coverings. Apparently beekeepers can find feral hives by looking for Cadarghis in native bushland.
Could these trees mean that our SE Qld Trigona bees are doomed for all practical purposes? Do we know which of our native plants depend on the Trigonas for pollination? Are these plants also, therefore doomed to extinction? Aaargh!!!!

    Bookmark   November 1, 2006 at 5:42AM
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Wooroonooran(NE, NSW.)


I think Greg is the best person to be asked this question.

Regarding Trigona, I wouldnt be alarmed at all.
If Greg would reply to my question about his post, then he might want to answer yours too!

Best regards from Kris

    Bookmark   November 1, 2006 at 6:19AM
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Stingless bees are divided into two families called Trigona or Austroplebeia.

There are ten named species in Australia. The three main species are-

Austroplebeia australis which are found in Southern and Western Queensland. They are very difficult to locate, as their activity is limited to warmer days. They are also very timid in character.

Trigona carbonaria are found in Coastal Queensland and as far south as Bega in NSW. They are relatively common in most locations, being able to adapt to a wide variety of nest trees. These little bees are very active during all seasons and are excellent for crop pollination. This species is reasonably common in bush areas without cadagi trees.

Trigona hockingsi are found in Northern Queensland. These native bees are the most powerful of all and can coexist with Cadagi trees. They are very difficult to keep in the cooler regions.

Information supplied by
Russell & Janine Zabel

I hope that this answers your questions.

You should check out their web site for some great info on stingless bees.

    Bookmark   November 6, 2006 at 11:11PM
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gardenlen(s/e qld aust)

the last time i chatted with russell when i bought a hive of bees from him, he was adamant that the cadagi should be gotten rid of. initially when we where moving to rural we where wanting a rapid growing tree for the conditions and thought the cadagi would be good, but not after that chat.

and after having the bees in suburbia before we went to rural they must have been getting to cadagi trees somewhere as they where gumming up their opening in the box.


    Bookmark   November 7, 2006 at 2:00PM
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trish_g(SE Qld Aust)

Thanks for the reply. Greg. So I suppose that means that Trigonia carbonaria is on the long list Australian natives due for extinction, together with all those plants which refuse to be germinated by anything else but their specific little bee.
With the push to introduce bumblebees into mainland Australia (so we can buy cheaper tomatoes. They'll never escape from the greenhouses, will they - even though they've done it already in Tasmania!) we do urgently need government money spent on research into insect pollination of natives. The pollinators of the vast majority of our plants are just not known.
Wooroonooran, your comment that "To do the right thing, everyone must plant only what occurs/ed in the Regional Ecosystem/s that occur/s on their property, otherwise they are introducing a plant to a new location where it shouldnt be" is very much to the point.
My comments are:
First - if we knew more about our local natives, we might find that there are more gardenworthy plants among them than we had realised, and choose them more where we're happy to have any old plant so long as it has the characteristics we want - feature tree, good screen, and so on. The difficulty, in such a large country, is finding the information as to what is locally native. One needs to be quite proactive to get hold of it, especially outside the capital cities. General books on growing Australian natives can leave us with a false impression. People who have picked pretty plants out of such books in the belief that they are doing the right thing by the environment, and then find themselves copping heaps from those with higher knowledge, are understandably cheesed off.
Second, we all like to grow introduced plants. There is really no difference, in a ecological sense, between growing roses and poinsettias, Norfolk Island pines, Lord Howe Daisies, and Kangaroo paws in Queensland, or even in growing plants that ocur naturally just a few hundred kilometres away. We all try (I'm sure) not to grow the obvious weeds from other parts of Australia. It is more environmentally correct to grow exotic plants that we feel are not going to escape into the bush.
However, as long as gardeners garden, there are going to be some apparently "safe" plants that will turn round and bite us on the bum 20 years later. We can only do what seems right at the time, keep an ear to the ground for new discoveries re weed potential, and be prepared to remove garden favourites when their dark side is first glimpsed, rather than insist on complete proof.
Thirdly, much of what gardening is, is to plant things from elsewhere. I don't mind this where people can choose a Australian plant because they really want that plant. What gives me trouble is the "natives" that are planted in good faith by so many Austalians including me, because we are restricted to the easily available plants in nurseries. In the case of Eucalypts, a local native gumtree might do the job just as well, AND be...

    Bookmark   November 9, 2006 at 7:06PM
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sweeney(Brisbane Aust)

There is a minor sawmilling benefit from Cadagi, E. or C. torelliana because the timber is durable in high rainfall Tropical Qld, e.g. on the floor of a truck because the boards do not swell & buckle when wet. The sandpaper leaf was also useful for sharpening spears in the Cadagi Provenance on the western edges of the rainforests near Kuranda/Myola west of Cairns. The Count De Torelli was not successful in draining the Pontine Marshes with them and malaria continued. Has anyone seen tree remnants near Rome?

It is a major problem exotic weed tree and not just for gumming up the native bees in S.E. Qld, where it was widely planted as a "good idea at the time" in the 1970-80s. We have 60+ planted in 1989 and now proving a major problem growing around a school oval on the red soils east of Brisbane which ecosystem I believe was originally subtropical rainforest. Cadagis demonstrate extreme allelopathy and like Casuarinas, very little will grow under the canopy because of the anti growth chemical factors in the leaves, except of course many Cadagi seedlings. You should take care not to use leaf mulch from many Eucalypts but definitely not Cadagi because of the chemicals inherent.

    Bookmark   November 15, 2006 at 2:42AM
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Fascinating reading! C. torelliana are being planted here by the millions as wind break trees for our struggling citrus industry. We've found that windbreaks slow the movement of the Asian Citrus Psyllid, the vector for citrus greening's causal agent, Candidatus Liberiabactor asiaticus & the Cadagi tree is the species chosen as the first line of defense. I just planted 10 this evening for their screening ability because the local railroad built an intermodal freight terminal nearby and I don't enjoy the view of their equipment or lights. I wonder if we'll be facing a whole host of problems in a few years too. I've enjoyed the read this evening.

    Bookmark   February 27, 2014 at 10:34PM
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