Do you think plants speak?
Yes they speak, every living being looks for a way to express itself. However, I believe that the imaginary of speaking or communicating is wrong. There are different types of communication and not all of them have to do with human language or its words. We cannot anthropomorphize everything. We must give space to our imagination and our understanding, to seek new forms of communication.
If they did, how would they communicate?
Well of course it is in the reading that they communicate through waves imperceptible by humans. These waves go through your body so they can identify if there is a problem or verify that everything is okay. As mentioned, plants are like a human brain is a single body, it is impressive how they dictate their life and become overly intelligent beings compared to the imaginary we give them.
And what would they tell you?
I think they would try to explain to me about them, something like they would tell me their story. I would also believe that they would complain for not treating them in the way they deserve, they would even make a complaint that they are not a decoration of our houses. They are independent beings, but that the human chose to appropriate, not as the domestication of dogs, but as a theft of property. But on the other hand, I think we would talk about many things, I would also explain to them about humans and ask them to be patient with us, although that does not mean that we should change our way of treating them from now on.