You may believe or not. But plants are very sensitive. The famous scientist of India Sir Jagdish Chandra Bose has proved it already. Just arrange some light musics or classical musics besides your garden and see the effect after one month. You can talk to them also and make it sure that they will respond you in some way or other. To prove it talk them politely and they will show quick growth and their growth will be squized if you talk them harsly. They are just like a child. They need your love and affection and fresh environment for easy growth. You can use birth control pills at the root of the plants for its growth. Above all vegetable pills, cowdung etc are the best manures for the plants and friends for the soil at the same time.