You did not mention if your cats were mainly indoor cats or allowed to roam. It is certainly safer for your cat and wildlife to keep your cat inside. With indoor cats, you could grow safe plants such as African violets. Could those favorite but cat-toxic plants be used in hanging baskets that are hung out of reach? If your cats are particularly drawn to your houseplants, it might be a good idea to check with your veterinarian about their diet or about tummy troubles such as hair balls.
Here is a list of plants known to be toxic to cats:
http://www.cfainc.org/articles/plants.html
Cornell University has an interesting site that discusses plants and chemicals that are toxic to cats:
http://www.ansci.cornell.edu/plants/catlist.html
