The vineyard represents God's people. Jesus likewise utilizes the illustration of a vineyard or the idea of producing fruit in a number of his parables. In fact John 15 says that He is the vine and we are the branches and that"He cuts off every branch in me that bears no fruit, while every branch that does bear fruit he prunes so that it will be even more fruitful."John 15:2 The briars and thorns represent the works of the devil, like the tares in Jesus' parable of the wheat and the tares, or of the thorns in his parable of the sower. They may come in the form of the worries, riches and pleasures in life which distract us from producing ripe fruit. Jesus battles against the unnecessary distractions in our lives and in ourselves. Things which shade us from the Son and waste the water of life.
Or it may be that you are a brier or thorn, a weed in God's field. It may be that you are a false Christian and that God is marching against you to tie you up and cast you into the fires of hell. What should you do? Make peace with God. Come to Him for refuge. He will transform you from weed to wheat.
Who is the Israel which will bud and blosssum and fill the world with fruit? It is the Christians. For Christianity is the true Judaism. And it is in the process of filling the world with fruit.