Information
The Tree is the very first decoration and can be built in the Stone Age. It provides 18 Happiness at a cost of only 8 Supplies. You start off with three Trees in the game.
Like with all other decorations, the Tree does not need to be connected to a road.
Efficiency
+18 per tile[1].
Output Modifier
Your decoration can be polished to double the happiness provided to +36 for 12 hours.