A friend at church told me a story about his dad planting trees. He had Willow trees at the back of his property growing near a meandering creek. One day he cut a branch off a huge willow tree and walking over to some wet soil near the stream he stuck it in the ground.
Years later now that Willow cutting is a huge tree. The original is now gone. It died and was cut up years ago and the new one is now nearly the same size. It's funny how some things grow.
Jesus said in John 15: 5-6, "I am the vine and you are the branches. If a man remains in me and I in him, he will bear much fruit; apart from me you can do nothing. If anyone does not remain in me, he is like a branch that is thrown away and withers; such branches are picked up and thrown in to the fire and burned."
It is significant to notice that grape vines do not root; if you take a cutting off and stick it in water, it will not grow new roots. Grape vines are durable plants but the only way to grow one is straight from seed. You cannot make your own grape vine from one of the cuttings.
Grape vines need to be trimmed, they must be pruned; severely in fact; in order to be fruitful. A grape vine that is not tended will grow wild and unproductive.
Cuttings from a grape vine are not useful for anything. They cannot be used to make twine, they are useless to build anything with. They aren't even very good as fuel. When a vintner burns cut grape vines they do it solely to get rid of them and not for the heat they provide. They aren't useful for anything.
Jesus is unique in a way that truly stands alone. Here he is claiming to be irreplaceable. He cannot be imitated nor can he be duplicated. In chapter 14 of John, Jesus leaves no doubt: "I am the way, the truth and the life. No one comes to the Father except through me." (John 14: 6)