Beware the Australian Silk Oak
Photo by Gabriell McGinnis of T Town Tree Service.
I am writing to report on an unusual accident that happened to me on the job here in Arizona. I own/operate a tree and landscape service I founded in 2015 and am a professional tree climber.
On June 4, 2020, I removed an Australian silk oak tree (Grevillea robusta) from a residential backyard in Oro Valley, Ariz. I spent maybe 30 minutes climbing the tree and another 10 minutes bucking up the spar on the ground. The following day I started experiencing a red, itchy rash covering my chest, arms and neck areas. This quickly spread to my legs and back and was extremely painful!
After speaking with different doctors, I eventually ended up with a prescription for 250 mg of diphenhydramine (antihistamine) and 60 mg of prednisone (corticosteroid) per day, along with topical hydrocortisone, lidocaine and calamine ointments to aid with the skin irritation. I missed five days of work and finally got back to light duty/office management six days after exposure.
A consulting arborist, Jacquelyne Lyle, Certified Arborist and a docent at the University of Arizona campus arboretum, helped me identify this tree, which I was not previously familiar with, as it is not commonly planted in the Sonoran desert region. I know of a few specimens in Tucson. Lyle said she knows of maybe 10 of these trees in Tucson.
These trees do not reach their “full potential” in this climate. As is often the case with non-native shade trees grown here in the Sonoran desert, you can expect shortened life spans and dwarf-like growth.
On doing a little research, I found incident reports from Australia and New Zealand where woodworkers and arborists had experienced similar acute contact dermatitis symptoms after exposure to the sawdust of this tree. These symptoms can, in some cases, last two to three weeks.
Gabriell McGinnis of T Town Tree Service, who took some of the accompanying photos, was working for me on the ground that day. He did not have any allergic reaction to the tree, but also was not running a saw that day.
Just to follow up on my condition, it did clear up about a week after exposure and taking the prescribed medications. I feel fortunate I didn’t have to stay on the medication longer, and, of course, am stoked that the nasty rash is long gone! I will not be cutting a Grevillia robusta again! I for one am glad I didn’t scratch myself to death, and am happy to be getting back to any capacity of work so soon. Stay safe.
Victor Riquelme is the owner/operator of Big Olive’s Property Maintenance/Big Olive’s, LLC, in Tucson, Arizona.
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Thank you for the information! I was thinking a purchasing one of these trees but now have decied against it since I maintain all my trees myself, and never with as much clothing has you had on!
Hello. So sorry to hear you went thru that. Thank you for the cautionary tale. We just purchased a house in central CA with two silky oaks in the back yard. We had no idea what they were nor did our realtor estate agent. I wish I had found out what they were and the potential problems they could cause early on. My family suffers from various allergies and I have a very active Australian cattle dog. We want to remove them asap, especially since they are pretty old and in bad shape. Any advice on what to do about saw dust or anything else we should look out for? Unfortunately we have neighbors directly on all sides of our fences that this will affect too.
Amanda,
It is fairly well documented that Grevillea robusta contains a multitude of toxins in its leaves, wood, flowers, seeds, etc.. Your family and your pets should be ok as long as you stay away from prolonged contact. If you contract a tree service company to remove yours, make it a point to let them know that their workers should consider wearing protective clothing and masks/face shields, which they should plan to remove and have cleaned after they are done! Thanks for writing and stay safe!
Victor Riquelme
Big Olive’s LLC
I am a wood carver, and made a few spoons out of this wood and developed a red, itchy rash covering my chest, arms and neck areas. Needless to say I will never use this wood again.
These trees are native here in Australia, and grow tall and beautiful. They don’t require maintenance here, and are food for australian bat super-pollinators and many native parrots and honey eaters. It is well known in Australia that humans can experience allergic reactions when cutting into these trees. Proper protective clothing should always be worn. These are otherwise excellent trees to support the natural ecosystem. Cheers mates!
We have a large one in our backyard and our dog has had continuous itching and skin rashes almost his entire three years of life here. We thought it might be caused by food and have tried many different diet regimes to no avail. We thought it might be industrial fallout (which we get from a steelworks about 12km away), but that has improved over the years with tighter pollution controls implemented. It’s costing us about $7 per day for medication to try to reduce his itching. Our previous dog didn’t have any skin irritations even when the pollution was worse. It seems this one is particularly sensitive to toxins. After reading about the dermatitis caused by Silky Oak, I blocked off the area under the tree a few days ago and he has not been scratching anywhere near as much since then. It certainly looks like the Silky Oak is the cause. I will be seeking Council permission to remove it. At least the timber is worth quite a bit and I can sell it to woodworkers who are game to work with it. It’s attractive timber.
Posted by TCIA Staff on behalf of the author, Victor Riquelme: John, I am sorry you and your pup had to go through all of this! A chemical compound called Tridecylresorcinol seems to be what is released by some different species in the Grevillea genus that can cause contact dermatitis. You may consider keeping the area under and around the tree cordoned off from pets for a season or two after the tree has been removed as a safety precaution. Trace oils, leaves, and dust can remain for a period of time though should eventually decompose.
Regards,
Victor Riquelme
Thanks for your comments Victor. I made a habit of regularly raking up the leaves etc. from this tree because they damage the grass when decomposing, but they constantly shed leaves and these are what our dog has been in contact with. Our tree is about 15m tall, and when I do remove it will cover the ground with a tarpaulin to catch the sawdust and other debris so I can safely dispose of it. I’ve made furniture and other items with this timber for many years without protective clothing or breathing equipment and have not been affected by it – I guess I’m one of the lucky ones – that’s why it took me so long to figure out it was a problem for our dog.