Many people have asked "why does my cat eat my plants?", or "why does my cat eat grass and then throw up?" I have seven possible motivations behind this feline behavior....
Boredom – If the cat’s environment is not stimulating enough they may eat plants, (among other things) for "entertainment".
Curiosity – Sometimes the scent of the plant is curious to the cat and leads them to want to taste it.
Movement – Maybe your plant is moving in the breeze of the air conditioning and looks like an enticing game of prey play.
Regurgitation – Cats throw up after eating grass or plants because they lack the amylase enzyme needed to digest the starch/vegetable/plant matter. They instinctively know this and they may feel the need to throw up to get rid of hairballs and other things they can’t digest (fur, bones, feathers, etc.)
Folic Acid – Maybe your cat is eating your plants because they are craving folic acid, which is found in the juices in some grasses. Folic acid is an essential vitamin for cats and if it is deficient in their food, they may feel the need to get some.
Laxative – Perhaps some of the grass that doesn’t get thrown up acts like a fiber and helps to clean out their system.
Mucus – My own hypotheses….Your cat's esophagus, stomach and intestines are lined with a mucus that protects it from the acids used to break down food. That mucus is generated more when a cat is chewing prey, versus eating commercial cat food. That, combined with a general lack of hydration (due to kibble feeding), may result in an unhealthy, or thin, mucus coating, and lead to an irritated stomach. Maybe the cat’s chewing of the leaves creates more mucus, or maybe their stomach is hurting from the acid and they think the regurgitation will help soothe the pain.
Many plants are toxic to cats so be sure to check the Humane Society's resource guide found here.