If any of you still want to know how to make a tree revival system (or any destructible, for that matter), you just need 2 triggers.
Initialization
Events
Map initialization
Conditions
Actions
Destructible - Pick every destructible in (Entire map) and do (Trigger - Add to Revive Trees <gen> the event (Destructible - (Picked destructible) dies))
You can add a condition or two in there if you only want a certain destructible to revive.
The second trigger is simple enough.
Revive Trees
Events
Conditions
Actions
Wait 15.00 seconds
Destructible - Resurrect (Dying destructible) with (Max life of (Dying destructible)) life and Show birth animation
The resurrect time is modifiable by editing the wait time. Yes, this does work and I've tested it.