When cats have a limited choice of plants to chew, this can lead to disaster as they may eat a poisonous plant.
Cats are obligate carnivores, so they must eat meat to survive and they will seldom choose to eat vegetables if offered them, but they do go outside and chew grass and perhaps other herbs.
This may be a way of dealing with parasites, aiding digestion or enabling them to eliminate hair balls. If there is nothing available which would seem an obvious choice, such as grass, they may feel the need to try houseplants or cut flowers.
This is where they seem to lose their sense of self-preservation and chew things like members of the lily family, which are very poisonous to cats. Young kittens too may like to sample things just like small children and this can lead to all sorts of trouble. If your cats are sampling plants indoors it's advisable to get some cat grass or cat mint or catnip for them to chew safely.
There are only a few very poisonous plants that you should avoid, mincluding lilies, being the main one.
Poisonous plants to cats