The fable, in the first reading, by Jotham reflects a strong rejection of the institution of the monarchy.
While the olive, fig and vibe are common but are considered prized trees in Palestine, the buckthorn, although it produces beautiful flowers, is viewed as bring worthless and a nuisance because of its thorns.
The key point of the fable is that only the worst and least qualified person is likely to accept the crown. Jotham's speech is aimed at the citizens of the city of Shechem who have not acted in an honorable way when they made Abimelech king. Jotham utters a curse against the people of Shechem and Abimelech.
The psalmist points out that if there is a king to be chosen, then it is God who makes the choice. After all, it is God who will care for, protect and bless the king with wealth, success and health. It is not for men but God to make the choice. The gospel passage reflects a similar message today. It is the land owner of the vineyard who decides on his workers and the amount of money they are to be paid.
However, at the end of the day, those who had worked longest are unhappy that they are paid the same amount as those who came later. But the land owner reminds them as to who is in-charge. The readings remind us that if we say that God is in-charge, then we have to allow Him to take control of every area of our lives. The question is "Can we?"
Lord, take control of my life.