The only natural way we found was to keep all live plants OUTSIDE. Honestly we cannot have live plants in the house - Charlie either tries to eat them or knocks the vase of flowers over.
I have lots of houseplants, and grow cat grass for my kits to keep them away from the other plants, however, every once in a while there will be a plant that is irresistable to a kit, so out it goes.
Have to keep my aloe vera (Max's fave, makes him vomit everywhere) and ponytail palm (Ginger's fave, just upsets me because it could hurt her intestines with its sharp edges) in a room the cats are kept out of.
I sell cat grass seeds on eBay, my thread is in Member's Marketplace, if you're interested in giving cat grass a try.
I keep grass for my boy but he still likes to nosh on my plants. The philo, which is bad for him, I keep in a hanging basket, and he ignores it. On the shelf that he can reach, I have mostly spider plants that I've heard are not harmful, and I don't really mind if he noshes on them.
If you want to keep your plants away from your cat, then they have to be someplace he isn't allowed (nowhere in my house) or outside. I think it's impossible to keep the cat away if the plants are accessible.