Eating Grass & Plants

Cats are obligate carnivores, which makes their enthusiasm for chewing grass look like a contradiction. It is not. Grass-eating is recorded in wild felids as well as house cats, and a large survey of over a thousand cat owners found that the great majority of cats eat plants regularly, with most appearing perfectly well before and after.

The old explanation — that cats eat grass to make themselves sick — does not survive contact with the data. Only around a quarter of cats vomit afterwards, and most show no signs of illness beforehand. Vomiting looks more like a side effect than the purpose.

Better explanations are on offer. One is parasite control: chewing fibrous material increases gut motility and may help sweep intestinal parasites along, a benefit that would have been meaningful to ancestral cats and is retained as an instinct in modern ones. Another is that indigestible plant fibre helps move hair and other debris through the digestive tract, reducing hairball problems. Grass also contains small amounts of folic acid and trace nutrients, though probably not in quantities that matter nutritionally.

The behaviour becomes a problem only when the plant is the wrong one. A cat that wants greenery and can only find a houseplant will eat the houseplant, and a great many popular indoor plants are toxic. Lilies are the extreme case — every part of a true lily, including the pollen and vase water, can cause fatal kidney failure in cats — but dieffenbachia, philodendron, pothos, sago palm and tulip bulbs are all dangerous too.

The practical answer is not to stop the behaviour but to redirect it. A pot of cat grass (usually wheat, oat or barley grass) or a tray of cat-safe herbs gives a cat somewhere legitimate to chew, and typically ends the assault on the houseplants within a week or two.