According to the American Society for the Prevention of Cruelty to Animals (ASPCA), chrysanthemum plants, or mums, are poisonous to dogs. They may cause vomiting, diarrhea, clumsiness, increased salivation and skin inflammation. If a pet ingests mums, the ASPCA advises that a local veterinarian or the ASPCA Animal Poison Control Center be contacted immediately.
According to PetMD, chrysanthemums commonly bloom in the fall and the plant's flowers, stems and leaves can all have toxic effects on both dogs and cats. Foxglove, daffodils, autumn crocus, garden calla and clematis are other plants that are known to be potentially toxic to pets. Toxic plants should be avoided in landscaping, where pets are free to roam, while indoor potted plants should be kept high enough so that they are not easily reached.