Jesus compared his kingdom to planting a garden many times. In one story, the farmer plants seed and then waits. One day, the plants grow and bear fruit.
We probably understand a lot more about germination and plant growth now. In Jesus' day, it was a mystery. It happened out of sight. And they did not know how to control the growth. God's kingdom is similar, because it grows in the hearts of people. It is out of sight. And people cannot control what happens in someone's heart.
For someone to choose to follow Jesus and become part of his family, there must be something that affects their hearts. God's word is planted in a heart and grows. it is God who causes the growth. We can apply truth -- by sharing God's word and obeying God's word -- and pray God causes it to grow. And it can grow until it is ready to reap.
Our part is to plant, pray and reap. Planting is the application of truth. Praying is agreeing with God's work to grow his seed and to hinder Satan's work to steal the seed. We can't hinder Satan's work. We cannot cause the seed to grow. And in reaping, we are accepting and celebrating the work God has done. We are witnesses of God's work.