Are Evergreens Poisonous to Cats?

When most folks think of evergreens, they think of Christmas trees. In most cases, popular Christmas tree species, such as blue spruce and Douglas fir, are not poisonous to cats, though ingesting sharp needles can wreak havoc with a cat's digestive system. Other species of pine tree, however, particularly Norfolk pine, house pine and Australian pine, are toxic to cats. Symptoms of pine toxicity in cats include vomiting and depression, and regurgitating sharp needles can be dangerous.

Another popular yuletide evergreen is holly. Like pine needles, holly leaves are sharp and can damage a cat's intestinal system if swallowed. Moreover, certain types of holly, such as English, Japanese, Chinese, Oregon and Christmas holly, contain several substances that are toxic in felines. Cats that have eaten holly leaves or berries often drool excessively, smack their lips, and suffer nausea and diarrhea. Head shaking, depression and lethargy also are signs of holly poisoning in cats.

Not all species of hemlock are toxic to cats. The Canada and Carolina varieties, for example, are not poisonous. However, certain species of hemlock are toxic to cats, particularly cowsbane and spotted hemlock, also known as poison hemlock. Though typically an outdoor plant, hemlock sprigs sometimes are used in floral arrangements. If the hemlock is dry, the risk of toxicity lessens. However, symptoms of hemlock poisoning can develop within minutes, and may include muscle tremors, loss of coordination, excessive drooling, panting, diarrhea and muscular paralysis.

Boxwood is one of the oldest and most popular garden ornamental plants in the United States, and many an outdoor cat, unfortunately, has sampled this venerable evergreen. Though typically not fatal if ingested, boxwood plants can cause vomiting and diarrhea in cats as well as dogs, due to the presence of alkaloids in the leaves.