The God, the life in us, pervades all living beings, be they plants or animals. Hence, they are all regarded as sacred. Human life on earth depends on plants and trees. They give us the vital factors that makes life possible on earth: food, oxygen, clothing, shelter, medicines etc.
Hence, in Bharat, we are taught to regard trees and plants as sacred. Hindu scriptures tell us to plant ten trees if, for any reason, we have to cut one. We are advised to use parts of trees and plants only as much as is needed for food, fuel, shelter etc. we are also urged to apologize to a plant or tree before cutting it.
Certain trees and plants like tulasi, peepal etc., which have tremendous beneficial qualities, are worshipped till today. It is believed that divine beings manifest as trees and plants, and many people worship them to fulfill their desires or to please the Lord.
From www.balagokulam.org