Angus StewartRed flowering gum

The red flowering gum, Corymbia ficifolia (formerly Eucalyptus ficifolia) is one of those trees that really grabs your attention when it’s in full flower, like very few other flowering trees can, perhaps with the exception of the jacaranda or the Illawarra flame tree.

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However, one of the ongoing problems with the red flowering gum has been that it’s always been grown from seed in the nursery industry in the past. When it did flower, after 5 to 10 years, the colour varied enormously as there is a great deal of genetic variability within this species. Not only does the colour vary, but the height of the tree can vary from a 10-15 metre substantial tree to a mallee form that’s no more than a couple of metres in height – a form which does have its advantages in the smaller gardens of today. One of the exciting developments in horticulture in recent years has been the development of the red flowering gum to make it more predictable and amenable to garden culture.

Corymbia-colour-forms-010Before I talk about that, though, I’d like to talk about the botany and the name change from Eucalyptus ficifolia to Corymbia ficifolia. The reason why the group of gums that include the red flowering gum were separated from Eucalyptus were that there are considerable differences. Corymbia are generally known as the bloodwoods and they have a special characteristic of being terminal flowering, with all those big sprays of flowers held on the end of the branches, which can be seen from a very long distance away. Many of what have remained as Eucalyptus flower way back inside the canopy on the axillary buds, unlike the terminal buds of Corymbia. Indeed, many people are surprised to hear that all gums are ‘flowering gums’; the red flowering gum just holds its flowers where they can be easily seen. Corymbia-colour-forms-005Corymbia shares this terminal flowering with Angophora, sometimes known as the apple gums, of which the Sydney red gum, Angophora costata is probably the best known in cultivation. The botanists faced the dilemma that Corymbia gums were more closely related to Angophora, both being terminal flowering and sharing some other characteristics. Being closer to Angophora, it was either include everything within the one genus of Eucalyptus, or split off the bloodwoods and create a separate group for them sitting in between Angophora and Eucalyptus.

Corymbia-colour-forms-003Which brings me to the genetic improvement of the red flowering gum, a brilliant but unreliable species, in the genetic sense that you don’t know what you’re getting! One of the more amazing projects that I’ve seen in my career as a plant breeder happened up in Queensland. A fellow by the name of Stan Henry, a retired horticulturist, wanted to grow a red flowering gum in his home garden but he was in the humid climate of coastal central Queensland. He watched a number of his Corymbia ficifolia die from the heat and humidity, and from the leaf spot that they tend to get when they’re grown in Sydney and further north (you can grow them but they look very ratty and not a good garden specimen).

Corymbia-colour-forms-007The strategy that he then chose was to hybridise Corymbia ficifolia, the red flowering gum from around Albany in south-west Western Australia with the swamp bloodwood, Corymbia ptychocarpa from northern Australia, which has the same spectacular terminal flowers common to all the Corymbias, but is obviously much better equipped to cope with the humidity and heat of northern Australia. By crossing those two species together, we get a group of hybrids which has been marketed as the Summer series – ‘Summer Red’, ‘Summer Beauty’ and ‘Summer Snow’, a white variety. Corymbia-colour-forms-001By and large it’s been quite a successful series when planted in gardens up and down the east coast, from Melbourne through to Queensland. Hybridisation is one way to go, and I like to think of what he’s done as a wonderful reconciliation, a sort of ‘east meets west’, between the swamp bloodwood from the east and north east and, from the other corner of the continent right down in the south-west, the red flowering gum. That’s where I think plant breeding really does have a place in modern horticulture; to combine the outstanding features of two different species to come up with a plant that has all the right attributes to be a successful garden plant.

Corymbia-colour-forms-006One of the issues with all the selections, whether they’re straight selections of Corymbia ficifolia or hybrids like the Summer series, is that they are difficult to propagate by cuttings – too difficult for commercial production. The way that they’re propagated now is by grafting onto the rootstock of a hardy member of the Corymbia group, such as the spotted gum, Corymbia maculata, or the red bloodwood, Corymbia gummifera. Finding the right species to use as a rootstock for different areas has become one of the key challenges for the selection and improvement of the Corymbia group, and in particular the flowering gums.

Corymbia-colour-forms-002The second wave of improvement of the red flowering gum has come about through the selection of different clones of the red flowering gum though the hundred years or so that this plant has been in cultivation. In southern Australia, from Perth across to Melbourne and up the southern coast of NSW, Corymbia ficifolia is quite a reliable species in its own right. Having been grown from seed, there’s all sorts of variation, so various nurseries have selected their outstanding forms of Corymbia ficifolia and we’re now seeing some interesting new cultivars emerge from that work. ‘Wildfire’ is one the oldest selections, and there are new ones called ‘Baby Red’, ‘Baby Orange’ and ‘Calypso’. Corymbia-colour-forms-009They’re all slightly different in both flower colour and plant height, so it’s a matter of going out and finding out what is available from your local garden retailer. There will be a continuing series of new selections in the future as we get more confident with the grafting of red flowering gums in its various colour selections and finding the right rootstock partner.

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The red flowering gum is one of our most iconic Australian species in cultivation, and through some judicious genetic selection and breeding work, we’re now starting to see cultivars emerge which are going to be more reliable – as far as knowing what flower colour and height you’re going to get. Hopefully in the future, you’ll be able to find anything from a 2 metre shrub to a 15m tree to match your garden requirements. So if you’ve ever planted a seedling tree and been disappointed, have another look as more new colours and forms emerge.

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34 thoughts on “Red flowering gum

  1. fran adams on said:

    I would like to be sure just when is the best time to prune red flowering gum after it has flowered. My tree doesn’t bloom in one burst of colour, but just several branches at the one time, over a period of approx 6 weeks.

    • Hi Fran – you don’t really need to prune red flowering gum as it should grow into a naturally bushy shape. When the tree is small, it can be a good idea to prune off the old flower heads so that the tree doesn’t put a lot of effort into the developing those big gumnuts when you want the whole tree to be growing bigger – unless of course you want them!

  2. Shane Goodwin on said:

    Hello there – I have 5 beautiful red flowering gums on my property in Melbourne. They are all in great condition and have just turned 100 years. I am wondering what the life span of these trees will be as they greatly enhance the property.

    Thank you……Shane

    • Hi Shane
      I agree with Catherine, the trees can potentially live for hundreds of years. Just try and keep competition in the form of lawn away from the trees and look out for pests such as borers and curl grubs and you should have decades of pleasure to come.
      Cheers
      Angus

  3. HI Shane – lucky you! They must be spectacular trees. Angus is on tour in Europe so he won’t be able to answer you for a few weeks. But as many Eucs and Corymbia live for hundreds of years, I see no reason why yours shouldn’t keep on going. The only threat would be long term drought. We often forget to water our big old trees, assuming they can cope with anything but the long droughts we’re experiencing in SE Aust could be too much for them. If you can spare the water, I’d give them a long drink if you can.

  4. Mrs. Mary van Leeuwen on said:

    Hi there, Angus! In our front garden we do have a red flowering gum; only, it has not flowered for some years now. Maybe one or two flowers, one here and one there! There are lots of dead branches on this tree! Should and could I trim this tree, if so what would be the right time to do this? And when I do, will it then benefit from the trimming it will get, and start producing flowers again??
    Hopeful!
    Regards, Mary.

    • Hi Mary
      The tree can certainly flower again. The best time to prune is around January Feb after its normal flowering time. However, as it is not flowering now I would wait until spring and then prune all the dead wood out and feed it with a native plant fertiliser with the aim of getting some new spring growth that may flower for you in summer. If not then, it should flower the following year. Good luck!
      Cheers
      Angus

  5. Jim Wright on said:

    G’day. I have potted 20 red flowering gums that I purchased from a nursery in Dural NSW. I live in Mackay Quensland and the plants have done very well up until now. Suddenly they have been simply dying. The leaves just dry out and the plant dies.
    Any idea what is wong?
    Regards
    Jim Wright

    • Hi Jim
      How long have you had these trees? Without knowing that it is a bit hard to say whether it is a problem that arrived with the trees from the nursery. If you have had them for quite a while then I suggest it is a soil borne problem. This could be curl grubs eating the roots or perhaps root rot killing the root systems. More information please?
      Cheers
      Angus

  6. Anna on said:

    An entire stock of of hybrid Eucalyptus ‘Summer Red’ Corymbia ficifolia x C. ptychocarpa grafted on Corymbia species rootstock arrived at the nursery I work in and all did the same. It is not about water as these plants were watered and in afternoon shade. They were initially pruned and treated and off cuts destroyed. The pots bounced back by late April, but were still decaying from tip to end leaf. I’m only a worker and the whole stock have now disappeared.

    • This certainly sounds like something such as curl grub. But hard to confirm without seeing the plants first hand!
      Cheers
      Angus

  7. Glenys on said:

    Hi, Angus, we are thinking about planting a red flowering gum. How does one check for curl grub and how can it be controlled?

    • Hi Glenys
      The best way to check for curl grub is to examine the root system by taking the root ball out of the pot and observe.
      Cheers
      Angus

  8. Mike Shaw on said:

    Hello, Could you possibly tell me where I could purchase Corymbia Ficifolia Summer Red, Summer Beauty, Summer Glory and Summer White in Queensland?

    Thank you.

    • Hi Mike
      I have just seen the Summer series on sale at Fairhill Nursery at Yandina. Nielsens Native Nursery in Brisbane also has stock from time to time.
      Cheers
      Angus

    • Tricia on said:

      Summer Red seems to be constantly available at Neilsens on the Beenleigh-Redland Bay Road (about $60.00). I purchased one from Big W about 2 years ago for $38.00 but Big W (at least at Upper Mt Gravatt) no longer seem to stock them.

  9. John on said:

    Hi Angus
    You may be able to help me, I planted two Summer Red hybrid eucalypts last Spring and we have had a very wet winter, I live South of Adelaide on the coast. The trees are about 180cm tall. They are making plenty of new growth at the moment, but on one of them all the new growth is very yellow. I thought there may have been a lack of iron or similar so gave the tree some chaleted iron. No sign of it working yet. Am I on the right track or have you any other ideas for me. I would appreciate any help you could give me

    Cheers
    John

    • Hi John
      I think you are on the right track. Perhaps try watering on some iron sulphate, say a dessertspoonful to a 10 litre watering can if you are still not getting a response to the iron chelates.
      Cheers
      Angus

  10. I have a six foot flowering gum in our garden and is not doing so well in the last few years. less flowers and dont seem to be getting any new leaf growth. The ends of the branches where the flowers were are dieing.
    Could the tree be getting to much water. We have it built up on a ground mound about 10 inches above the surrounding ground level. We have cannons planted around the base could this be the problem. Sure hope some one can help.

    Thanks Robert of Tasmania North.

    • Hi Robert
      The tree is under some sort of stress to the roots. Could be root rot or perhaps curl grubs eating the roots. Have a scratch around underneath the tree to see if there are any curl grubs there. If not it could be root rot in which case I would treat with antirot fungicide. Good luck
      Cheers
      Angus

      • Thanks Angus will be checking this week end and let you know the out come

  11. Max on said:

    Hi
    Flowering gum just up and died. Is one of three. Others doing well.

    • Chris on said:

      Hi Max and Angus, our 10 yr old, 3m flowering gum is looking like its almost on its death bed too. We are quite sad about this and hope that maybe there might be a solution to help this lovely tree come back to our garden. Regards Chris.

      • Well there could be a couple of causes. One is root rot. You could try treating the healthy ones with antirot.
        The other possibility is that if your trees are grafted then it may be failure of the graft union which you would see at the base of the tree. Inspect the graft union and see if it is healthy. If there is not a good connection or there is sprouting below the graft union from the rootstock then that is the cause

  12. Adrian O'Brien on said:

    I have a red flowering gum in the front northern facing yard about 25 foot high. It has been doing well until last year when the local possum population decided that it was quite tasty!! However since then (and it is still providing local possum tucker) it has developed a white frothy substance in the end branches which then drips the froth and a clear liquid substance all over the place and is quite unpleasant and unsightly. It looks like someone has spat into the tree branches. I can send a photo if it helps. Any comment would be much appreciated.

    • Hi Adrian
      Sounds like you have a case of spittle bug. It is a sap sucking insect inside that froth. Hosing it off with water generally does the trick.
      Cheers
      Angus

  13. george vassallo on said:

    I have purchased a grafted summer red a year a go, the tree has not
    grown very much the leaves are green and healthy but now all the buds
    have just fallen off , it is in a pot and the tree is about 900mm tall can you please help

    • Hi George
      There could be a few reasons why this has happened. If the plant has dried right out in the pot with the hotter weather the flower buds would be the first thing to drop off. Also root rot could cause those symptoms in which case I would treat the tree with Antirot. You may be better to put the plant in the ground in a sunny well drained spot.
      Best regards
      Angus

  14. Judy on said:

    Hi Angus
    I planted a “Summer Red” about 7 years ago and the plant is doing particularly well, except that the flower buds drop off before they open. The tree currently has a lot of flower buds, but I rarely see an open flower. I live in Sydney’s Inner West, where there are a number of street plantings of the different Summer varieties that all seem to flower better than mine. Do you know what could cause bud drop on these trees?
    Regards
    Judy

  15. Linda Cummings on said:

    We have recently moved and have two lovely flowering gums in our front garden. Sadly one of them has developed a sort of rust on the leaves which has spread quickly over the tree. The tree is about 1.5m tall. We have pruned it back hard. What else can we do to fix the problem? We would appreciate any advice.
    Regards,
    Linda

  16. Sally on said:

    Hi and Happy New Year to all.
    November 2012 I planted Corymbia ficifolia Petite Orange as a feature plant in a slightly raised bed among thriving leucospermums and leucadendrons. It flowered last summer and is about to burst into flower again. I had hessian around it for its first winter as we get a few frosts. (I live in NSW on the far south coast, about half an hour inland.) Last year’s leaves look a bit motley (I probably should remove them) but there is plenty of new, healthy growth and the tree is now about 60cm tall. However, there appears to be suckers popping up, up to a meter or so away. I’m assuming they are suckers and not from seeds the tree produced last season. If it is a problem now is it going to be an even bigger problem as the tree gets older and competes with surrounding plants? Can I deal with it by diligently pruning off the suckers!!!? Otherwise, should I remove it now while still small enough to relocate? I am wondering whether the cold might have stressed the plant a bit and be causing this.

  17. Pamela on said:

    Hi my husband just purchased one of these as I mentioned I would love a small one for our front garden unfortunely the tag on it says 6 – 15 metres is there any way of pruning it so it stays small or did we just buy the wrong one ? Thanks Pamela

  18. Cedar Wilde on said:

    Hi Angus,
    I want to grow some more red flowering gums from the seed of my tree (I know they may not turn out to be red as there are other gums in the area) When is a good time to sow the seed?

  19. Steven on said:

    How big is the root spread on the new style grafted summer red

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