I have seen Australian Silky Oak (Grevillea robusta) trees growing in rows on some farms around the country – learning much later that this is probably because they are sturdy and fast-growing here and so make good wind breaks. So many exotic plants make their way around the world for practical reasons such as this as well as for their beauty. The Silky Oak bears beautiful golden yellow to orange flowers shaped rather like a bottle-brush. These, combined with their straight trunks and moderately spreading crowns have made them a favourite street tree too – a number of streets in Grahamstown are lined with them – as they provide good shade.

I happened to be parked in a street lined with them when I noticed that the natural cracks in the bark of some of the trees were filled with termite tunnels. I have subsequently read that Silky Oaks are susceptible to termites that pack mud over their excavations into the wood.

You can see this clearly in the next photograph:

The fern-like leaves of the Silky Oak are dark green above and greyish-white or rusty-silk coloured beneath – which may have given rise to their other common name, Silver Oak.

As with the flowers of the Huil Boerboon (Tree Fuschia) the flowers of the Silky Oak drips with nectar, making a sticky mess on any vehicles parked underneath them during the blooming season. It is not flowering time now, but I noticed that a number of trees were exuding gum resin. Some of this was very fresh and literally dripped from one dollop of gum down to the next:

While other globules of gum were stiffer – probably older.

Stretched across some of the cracks in the bark – and covering the gum in places – were a number of tightly woven spider webs.

They are doubtless here to stay for I cannot imagine any debt-ridden municipality cutting down swathes of mature trees simply because views have changed and the silky oaks are now considered to be alien invasive trees. What they will be replaced with as they grow older is of more concern. Silky Oaks have been here for so long that they are considered to be naturalised – much as the Jacaranda trees have. A problem, however, is that, thanks to the easy dispersal of their seeds, they are considered to be particularly invasive in both the Western and Cape, KwaZulu-Natal, Gauteng, Limpopo and Mpumalanga.


43 thoughts on “SILKY OAK TREES

    • It is interesting to note that the trees along this particular street were probably never meant to be parked under: they line a street adjacent to what used to be a school and a chapel – now turned into an educational institution. On the opposite side of the street would have been a park – now a cluster of houses and a medical centre. Both attract several parked vehicles every day … good luck to them all when the trees decide to topple!


  1. I thought I was reading an Australian blog when I first saw the picture of the Silky Oak! There must have been quite a bit of botanical transfer over the years. The Jacarandas here have become such an iconic part of our city – especially when they flower so beautifully in November. Will they cut the tree down?

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    • I don’t blame you for thinking Australia -Silky Oaks were imported for shade, beauty and agroforestry and are now all over South Africa. I doubt if the tree will be removed unless it shows signs of collapsing. All of the trees looked sturdy enough to me despite the obvious signs of termite tunnels running up their trunks. Both these and Jacarandas are declared alien invasive trees and one may no longer plant them, although the mature trees may remain in situ.


  2. Perhaps we should negotiate with the termites to go sort out the trees invading our natural spaces and leave the stately old ones growing along Grahamstown’s streets to live out their natural lives.

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  3. What a fascinating tree! So much going on with that bark. Mainers grumble about people “from away” but eventually they accept them into the community. Perhaps the same thing has happened with the silky oak tree?

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    • There are so many of them here that, like the European (Common) Starling and the Jacaranda trees, the silky oaks are accepted even though the planting of new ones is discouraged.

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    • Al is hulle uitheemse bome word hulle al jare lank hier aangeplant. Ek weet nie wanneer julle die Silky Oaks gekoop het nie, maar deesdae word hulle nie meer by kwekerye aangebied nie.

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    • I’m interested to know how strong these trees are, do they fall over easily like black wattle or will they be sturdy.
      I have five very big trees in my paddock and wonder if my donkeys and ponies are safe around them. I’d appreciate any feedback. Tnx

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      • They are very strong trees, Kerry – providing they are healthy of course. The ones featured here must be sixty if not more years old and show no sign of falling over.


      • Many thanks for the info, we are in South Africa and these trees attract Alot of birds including owls and eagles. I think they are beautiful trees.

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  4. An old tree in a park where I used to frequent as a youngster was damaged during a storm last year, bringing down over half of that Willow tree. Its trunk was split in two and you could see Carpenter Ants scurrying in tunnels inside the tree and a man suggested that wood was infested for a long time and likely weak from the ant tunnels.

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