Grevillea is a vast genus within the Proteaceae family, encompassing over 360 species and numerous cultivars. Native primarily to Australia, these plants are celebrated for their spectacular and intricate flowers, often in vibrant shades of red, orange, pink, or yellow, and their diverse foliage forms. They are popular in gardens worldwide for their drought tolerance, wildlife-attracting qualities, and unique aesthetic appeal. Given this popularity and the proximity of pets to garden plants, understanding their potential toxicity is crucial for pet owners.
The primary concern regarding the toxicity of Grevillea to pets lies not in the plant's nectar or pollen, but in a specific compound present in its foliage, and particularly in its unripe seed pods and seeds. Certain species of Grevillea are known to contain cyanogenic glycosides. These are naturally occurring compounds that, when chewed and ingested, can break down in the animal's digestive system to release hydrogen cyanide, a potent and dangerous toxin. This is a defense mechanism the plant has evolved against herbivores.
The risk to dogs and cats from Grevillea is generally considered low to moderate and is highly dependent on the amount ingested and the specific part of the plant consumed. A dog or cat that nibbles on a few leaves is unlikely to experience severe poisoning. However, ingestion of larger quantities, especially of the unripe seed pods, seeds, or specific high-risk species, can lead to cyanide toxicity. Clinical signs of cyanide poisoning can appear rapidly and include dilated pupils, difficulty breathing, panting, bright red mucous membranes (gums), shock, and in severe cases, collapse and death. It is imperative to seek immediate veterinary attention if a pet has ingested a large amount of any Grevillea plant and is displaying these symptoms.
Information on the effects of Grevillea on exotic pets like birds and reptiles is less documented. However, the mechanism of cyanogenic glycosides is a broad physiological one, affecting many species that utilize cellular respiration. Therefore, it is prudent to assume that the plant could pose a similar risk to birds, small mammals like rabbits and guinea pigs, and reptiles if they were to ingest significant quantities of the problematic plant parts. As a precaution, access to Grevillea plants should be restricted for all pet species.
While not all Grevillea species possess high levels of cyanogenic glycosides, some are particularly noted for their toxicity. The most frequently cited dangerous species is Grevillea robusta (Silky Oak). All parts of this tree, but especially the unripe seed pods and seeds, are considered toxic and have been implicated in cases of livestock and pet poisoning. Other species, such as Grevillea banksii and Grevillea bipinnatifida, have also been reported to contain these toxic compounds. When selecting a Grevillea for a pet-friendly garden, it is wise to research the specific cultivar and err on the side of caution by choosing a known lower-risk variety.
