The game will look very poorly made, if I only use a small amout of objects. That will be a very sad forest
Yes I use Foliage.
I lag even if I remove everything but the trees, 150 trees and editor + game lags, everytime I look in the direction of the trees. 2 types of trees are used.
Do you use the foliage painting tool (instead of placing foliage by hand? Because the tool instances foliage meshes, which considerably cuts down on performance requirements. Also for larger landscapes it helps to create different levels with foliage/content, and then stream them (loads them if the player is near the related level streaming volume).