Some years ago I was a member of a model railroad club, I didn't own any rolling stock, I was only in it for the landscape and layout building. 
Anyhow, making forests was a large part of the landscape work and that gave me reason to consider the issue with height of trees and I realised that ALL available trees were severely undersized if they were to represent full grown trees, not talking redwoods or anything large, just plane Jane Swedish pine and fir, birches also grow taller than H0-scale layout bushes. 
Nature has a tendency of becoming very large .... 
Consider the trunk diameter of a large pine, 35 cm is sort of a medium size tree, the big ones are thicker, 35 cm would be a whole cm in 1/35th, a wooden pencil is 0.7 mm ....
The ones hitting 40 m will be thicker, over 2 feet diameter. 
My sister had two big ones taken down in her backyard and a local craftsman made chairs from the bottom ends.  

Image from the internet, the ones my sister have look a lot better. Ask google about stockstol.
2 feet in 1/35th is 1.7 cm (11/16 of an inch) ....
/ Robin