The term "geranium" in common horticulture can be a source of significant confusion from a botanical perspective. Most of the vibrant, potted plants commonly sold and grown as "geraniums" actually belong to the genus Pelargonium. True Geraniums are a separate genus, comprising hardy herbaceous plants often called "cranesbills." This distinction is critical because the two genera have different chemical compositions. When pet owners ask about the toxicity of "geraniums," they are almost invariably referring to the ubiquitous Pelargonium species, which are widely used in gardens, window boxes, and as houseplants.
Pelargoniums, particularly the common scented varieties like the Citronella geranium (Pelargonium citrosum) or the Rose geranium (Pelargonium graveolens), contain two primary toxic principles: geraniol and linalool. These are organic compounds classified as terpenes, which are volatile aromatic compounds produced by the plant, likely as a defense mechanism against herbivores and insects. While these compounds are extracted and used safely in diluted forms in perfumes and essential oils, they are highly concentrated in the plant's foliage. When ingested by cats or dogs, these essential oils and the plant's other constituents can cause a range of adverse gastrointestinal and neurological effects.
The toxicity mechanism involves the irritation of the digestive system and the potential to affect the nervous system. Geraniol and linalool are gastrointestinal irritants. Upon ingestion, even of a small amount, these compounds can cause inflammation of the mouth, esophagus, and stomach. The most common symptoms observed in both cats and dogs include vomiting, anorexia (refusal to eat), depression, and lethargy. In some cases, particularly with larger ingestions, ataxia (loss of coordination) or dermatitis may occur. Cats are often more sensitive due to their smaller size and their limited ability to metabolize certain plant compounds, making them potentially more susceptible to the toxic effects.
In contrast to the Pelargonium genus, plants from the true Geranium genus (Cranesbills) are generally considered non-toxic to both cats and dogs. These perennial garden plants do not produce the same concentration of volatile essential oils that make their Pelargonium cousins dangerous. While it is never advisable for pets to consume large quantities of any non-food plant, as this could cause mild stomach upset from the physical irritation of the plant matter itself, true Geraniums are not known to contain any specific toxic compounds that would cause systemic poisoning in companion animals. This highlights the immense importance of using precise botanical names when discussing plant toxicity.
