Can trees "communicate?"

I had one of those smile and nod conversations the other day. The person I was conversing with was explaining to me how trees can “talk to each other” and that modern science couldn’t explain it. There was one point in his conversation which I had heard in the past, the assertion was that when a tree is infected it sends out some sort of a distress signal and nearby trees try to build up their immunity to it. Is there any validity to his claims and specifically to the one I mentioned?

From here. So, some plants can communicate chemically, but I wouldn’t go so far as to call it “talking”.