Tom P, I seem to recall him referencing the trees or maybe thats what I interpreted from his writing style.
I can tell you this, Growing up in Chicago, I think I can recall my first idea for how to improve a hole and it was to plant a tree. Thinking hard as to why, I can only come up with "because it was tooeasy,or too open in that spot,and adding a tree,would create havoc,for those who went there":
Having come to that conclusion, naturally, without the study of GCA, I must now conclude that that line of reasoning was wrong. A rookie mistake, a fundemantal default place for the unsophisticated to go. While it makes sense that the trees do do all of those things I mentioned above, the sport is much bigger and much more complicated than the simple decision to plant trees. Maybe That's why they are often viewed as hiding a weakness in the design, because the thought ends there.