Tree generator around player

Hello fellow developers,
I am making a 3D open area game that takes place in a forest. Now the forest is big and there will be a lot of trees. But it will be really hard to manually place trees and creating them all over the forest might lag the game. So I’m thinking if creating a circle around the player that moves with the player. Now if the circle enters a place where there is not a tree, then a tree will be created and when a tree leaves the circle the tree will be deleted.
This is to keep a smooth gameplay and to make sure to get the maximum fps for best gaming results.
Please do help me in figuring out on how to make this work in the game.
Thanks alot!