why do horticulturist say talk to your plants ?

Answer 1

experiments have proven that plants are sensitive to external stimulii, so talking can improve the plants growth, health, etc.

I too, was skeptical, until I destroyed a houseplant by hanging it too close to the stove.
My roommate talked real pretty to it and the next day it was more vibrant than I had ever seen, and I would have sworn it was completely dead.

Answer 2

Some say speaking kindly to your plants will make them grow better. I am a horticulturist and I don't say this. I think the physical care is the greater influence of having well-cared-for plants. The benefit is perhaps therapy for yourself.

Answer 3

Plants use carbon dioxide to grow, which we exhale, and in return the plant releases oxygen, which is good for us. So a plant will receive more carbon dioxide then is naturally available by talking (or breathing) on your plants. I really dont think you will notice a difference in plant growth, but it sure wont hurt your plants to talk to them!