Orange trees will provide you with oranges when harvested. Each tree has 3 harvests, with a cooldown of 5 minutes between one and the next. They cost 300 coins in the shop and are unlocked once you get 30 mastery stars. The tree can be harvested right after the purchase however, it cannot be sold for coins or placed in your inventory once bought.
When it's ready to harvest, the tree will have ripe oranges all over. After you harvest it, it will show green oranges and orange blossoms. When you harvest it 3 times it will decay and you have the option to clean it (it costs 1 energy to do it) so, if you want more oranges, you will have to buy a new one from the shop.
Red Wood Planks can also be harvested from orange trees. Trees may produce 1 orange and 1 red wood plank or just 1 orange with each harvest.