From a botanical perspective, the common name "daylily" is the source of significant and dangerous confusion for pet owners. True daylilies belong to the genus Hemerocallis. Plants in this genus are highly toxic to cats and can cause acute kidney failure. It is critical to distinguish these from other plants that may have "lily" in their common name. For example, plants like the Peace Lily (Spathiphyllum), Lily of the Valley (Convallaria majalis), and Peruvian Lily (Alstroemeria) are not true lilies (family Liliaceae) but belong to different plant families altogether, each with its own toxicity profile. The focus of this guide is specifically on Hemerocallis species, which are common perennial plants in US gardens, prized for their vibrant, trumpet-shaped flowers that typically last only one day.
The exact toxin within Hemerocallis plants that causes poisoning in cats has not been definitively identified, but its effect is well-documented and severe. The toxic principle is present in all parts of the plant—flowers, leaves, stems, and even the pollen. For cats, ingestion of even a small amount, such as a few petals or leaves, or even drinking water from a vase containing daylilies, can lead to rapid-onset kidney injury. The toxin appears to target the renal tubular cells, leading to cell death and potentially irreversible kidney failure. The plant's biological purpose for producing this compound is not fully understood but may serve as a defense mechanism against herbivores. It is important to note that this specific reaction is unique to felines.
The toxicity of daylilies exhibits a remarkable species-specificity. This is a common phenomenon in the plant kingdom, where a compound harmful to one species may be harmless to another. For Hemerocallis:
Cats: As stated, all parts of the plant are extremely toxic to cats. There is no known safe variety or "non-toxic" Hemerocallis species for felines. The poisoning can progress rapidly from vomiting and lethargy to serious kidney compromise within 24 to 72 hours.
Dogs: In contrast, daylilies are generally considered non-toxic to dogs. The American Society for the Prevention of Cruelty to Animals (ASPCA) and other pet poison control resources classify Hemerocallis as safe for canine companions. While ingesting any plant material may cause mild gastrointestinal upset in a dog, such as vomiting or diarrhea, due to the irritation of the stomach lining, it does not cause the systemic, kidney-targeting toxicity seen in cats.
Hemerocallis is a diverse genus with thousands of cultivated hybrids, all of which pose the same risk to cats. Common varieties found in US gardens include the classic orange ditch lily (Hemerocallis fulva), as well as popular cultivars like 'Stella de Oro', 'Happy Returns', and 'Pardon Me'. Given the severe risk to cats, the safest approach for households with feline members is to avoid planting daylilies in the garden or bringing them into the home as cut flowers. If daylilies are already present in a garden shared with an outdoor or curious indoor/outdoor cat, pet owners should consider removing the plants or creating a secure, cat-proof barrier to prevent access. Awareness of the plants in your environment is the first and most critical step in ensuring pet safety.
