Dogs love to eat tender green things. Often dogs like to eat grass. Is your dog nibbling on the plants? Is this a new problem? Is this a new dog? First off I would put the plants up or put them in areas away from your dog.
There is a condition called pica, where the dog has a desire to eat dirt, or clay or chalk. This is not a common problem. But it does happen. Make sure your dog has nutricious, complete diet.
I would suspect this is more of a behavior issue. I think he has too much unstructured time which leads to him getting into mischief. If that is the case, he needs more creative activities. A Kong busy ball, where you can hide treats can provide lots of entertainment. Or a plastic milk bottle with something to rattle inside. Of course taking him on walks and giving him one on one attention is good too.
If you are looking for something to keep him out of an area, you need to have some sort of negative feedback when he gets near the plants. There are motion detectors that set off an alarm if he gets near the plants. I even have one that barks like a Rottweiler. Ideally, the negative feed back is more than you yelling at him when he is near the plants. If it is just you, he will soon learn to get in the plants when you are not looking or when you are not around. There are some flap traps you can set. They look like mouse traps, but they don't hurt the dog. They just have a load plastic flap that snaps when the dog touches the flap trap.
I hope you, your dog, and your plants all learn to play nice.