There are several trees available in Trade Nations to decorate your village:
Poplar Tree[]
Available in the first level. It costs 5g.
Spruce Tree[]
Available in level 3. It costs 80g.
Oak Tree[]
Available in level 3. It costs 10 mb.
"Oak Trees grant a bonus to the XP and Gold recieved from all shops by .4%"
-description.
Birch Tree[]
Available in level 5. It costs 120g.
Maple Tree[]
Available in level 7. It costs 160g.