Marigolds can be either non-toxic or mildly toxic to cats, depending on the type. The common "pot marigold" (Calendula officinalis) is generally safe and non-toxic for cats, while "French marigolds" (Tagetes species), which are true marigolds, can be mildly toxic if ingested in large quantities, potentially causing digestive issues like vomiting, diarrhea, drooling, and stomach pain. It is best to avoid growing French marigolds in environments where cats have access. If a cat eats a toxic variety or shows symptoms like excessive drooling or diarrhea, veterinary advice should be sought promptly.