Grevillea is a diverse genus of evergreen plants within the Proteaceae family, comprising over 360 species and numerous cultivars. Native primarily to Australia, these plants are celebrated for their unique and often spectacular flowers, which lack true petals and instead feature long, stylized styles that give them a spider-like appearance. They are highly valued in horticulture for their drought tolerance, attractive foliage, and their ability to attract nectar-feeding birds. With such a wide variety, from ground covers to large trees, understanding their interaction with domestic pets is crucial for responsible gardening.
From a botanical perspective, the vast majority of Grevillea species are considered non-toxic to both cats and dogs. This is a significant point of distinction from many other popular ornamental plants. The genus does not produce alkaloids or glycosides in significant quantities that are known to be poisonous to mammals. The primary concern for pets, particularly dogs, is not systemic poisoning but rather a unique and specific physical irritant present in some species.
The notable exception to the general rule of non-toxicity involves a group of cultivars, with 'Grevillea robusta' and particularly 'Grevillea 'Robyn Gordon'' being the most prominent. These plants, and some of their hybrids, produce and store a compound known as tridecyl resorcinol. This substance is a potent irritant and is the same compound responsible for the severe reactions associated with poison ivy. For dogs that chew on or ingest the leaves or flowers of these specific Grevillea varieties, this compound can cause severe allergic skin reactions and oral ulceration.
If a dog chews on a problematic Grevillea like 'Robyn Gordon', the tridecyl resorcinol can cause contact dermatitis. Symptoms are typically localized to the area of contact and may include intense redness, swelling, itching, and the development of blisters or rashes on the skin, muzzle, or paws. If ingested, it can cause significant inflammation of the mouth, lips, and tongue, leading to drooling, pawing at the mouth, apparent pain, and reluctance to eat. It is important to note that this is a contact irritant and not a neurotoxin or organ-damaging poison.
While the primary documented cases of irritation involve dogs, the mechanism of the irritant (tridecyl resorcinol) suggests that cats could also potentially be affected if they were to chew on the plant. However, cats are generally more discerning chewers of plants than dogs and are statistically less likely to ingest such material. For the majority of other Grevillea species not in the 'Robyn Gordon' group, the risk to both cats and dogs is exceptionally low. Nevertheless, it is always prudent to discourage pets from chewing on any ornamental plants, as individual animals may have unique sensitivities, and ingestion of plant matter can cause mild gastrointestinal upset simply due to the physical irritation of the foliage.
