As the name suggests, yucca plants are "yucky" for cats. Cats are drawn to eating plants. Unfortunately, cats do not know which plants are toxic. When planting your garden, eliminate the yucca, as it is harmful to cats.
The yucca plant contains the biochemical saponins, which is poisonous to cats. Saponins is also toxic to dogs and horses, and owners of all three animals should definitely reconsider planting yucca in the garden.
Cats that eat yucca plants suffer from vomiting and diarrhoea. If your cat is sick and you notice signs of chewing on your spiky yucca plants, chances are your feline has ingested portions of the yucca plant and is suffering from its toxicity.
Many plant varieties are non-toxic to cats and look much like a yucca plant. Certain palm and fern varieties mimic the yucca's leaves, and many other plants have white flowery stalks. These plants are cat-safe alternatives to yucca plants in any garden where they can acclimate. The American Society for the Prevention of Cruelty to Animals provides a list of non-toxic plants to substitute for your yuccas.
If you suspect your cat has ingested a yucca plant, take it to the veterinarian immediately. If you need to speak with an expert, the ASCPA has an Animal Poison Control Center hotline. For a fee of £42 as of October 2010, they can help. The number is 1-888-426-4435.