Dev's explanations about this question :
The rules are exactly the same for all trees, the only difference between "wild" trees and player-planted ones is, well, the act of their creation - first ones are planted "naturally", the second - by hand.
Player intervention will inevitably "move" the forest state either towards optimal state or away from it. If left unattended, the plantations that move the forest away from the optimal state will eventually die out. For example, in a forest that is supposed to have 1000 apple trees players are free to plant additional 2000 apple trees by themselves, but the "natural" way of forest development will resist those changes and the excessive apple trees will slowly (SLOWLY) die out if players do not restore their plantations
Source : http://steamcommunity.com/app/290080/discussions/0/276237094321633855/?ctp=2#c276237094331443312
and
Time will tell whether there are exploits like this or not, but right now it seems doubtful that players will be able to affect the balance in a significant way - it would require manually planting thousands and thousands of trees.
But more importantly - even if such a giant man-made plantation arises, the rate at which trees age (i.e. become bigger) will not change - in fact it never will, no matter what (I assume that this is what you mean by "forcing plantation growth down"?).
Nothing stops you from planting trees that you want, no matter what happens in other parts of the server, and nothing changes aging speed of those trees. In fact, the whole "sweet spot balancing" thing is there mainly to protect from forests that become so big in terms of tree numbers they cause lags (as was before, even if players planted nothing extra) and to generate forests that are visually pretty.
Also nothing stops players from manual creation of super overgrown forests, but that's players' choice and you will have to work to achieve that because the system will constantly push back.
Source : http://steamcommunity.com/app/290080/discussions/0/276237094321633855/?ctp=2#c276237094331666012