The Last Alliance has an article on making Mallorn Trees — those huge trees amongst which the elves live in The Lord of The Rings. The idea is that the trees are so large — and their branches so high that only the trunks come into play in a game.
Now, I don’t have much use for Mallorn Trees, but it occurs to me that the same technique also could be used to make the trunks of trees in, say, the Brazilian rain forest. You could use some of those Copplestone pygmies and Amazon explorers.