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.