A branch you get from the tree. You can harvest the tree for 10 times and then it needs water. Your neigbour can give your tree water and then you can harvest it again for 10 times. This you can do for max 3 times, then you tree will dry up and you need to chop him. To chop you need an axe. You can find the axe in the game while collect items, harvest your crops, in the chests at your land or your neighbours and as bonus for completing quests or the Arena.
if you don't