What does tree represent?

The family tree represents their stability and connection to their past. When the tree is stable and left alone, the family is strong. In the moments that the tree is threatened, so is the family’s connection. This is why they fight the most when Mirabel almost destroys it, especially when one considers that it was something their grandfather loved. This is why Merry chooses to stay at the family home even though her work is done. She wants to see that the tree - and, therefore, the family - can move on together after their grandfather’s death.