Trees are an essential natural resource giving your citizens logs.
An educated citizen that cuts down a fully grown tree will produce 3 logs, while an uneducated citizen will produce 2 logs. Trees that are not fully grown will provide fewer logs when cut down.
New trees can be planted by foresters working at a forester's lodge or by farmers working at an orchard. New trees will also spontaneously appear near other fully grown trees.
It takes two years for a tree to grow to full size. Trees will eventually fall over naturally and produce no resources.