Thanks, I have taken a few writing classes, and while it focused more on writing, I can't say they ever steered us away from "unreputable" sites. I can do more research if you'd like, but that's just what google brought me first. The general consensus of googles hits was that this was debunked many times. Not only for a poor testing practice, but because science does not label plants as having the 5 senses.
I won't just throw all that knowledge away from the collective facts of science just because this guy thought his plants were happy and sad, or understood threats of violence towards them. Sounds all very supernatural. I even found those links from a supernatural discussion forum. Even they were having a hard time believing it. They were discussing whether or not the carbon dioxide levels were different from talking to your plants, and that vibrations from your sound waves stimulated the plants more than your thoughts or moods. But that was just a non-scientific, supernatural forum.
They are with me though on one thing, what are the vegetarians supposed to eat now??