For my Endless Terrain Battlemaps - Heavy Forest, on an 11 x 17 map tile, I have about six trees on average in the map. While a regional view of the same terrain might show a blanket of trees and no ground, it depends on your point of view. I've been thinking however of creating some forest maps that show the trunks and roots of the trees and not the upper foilage at all, so use between trees could be more apparent.

It depends on your needs.

GP