Jesus taught many parables by the Sea of Galilee, with several focused on seeds and agriculture. Matthew 13 gives the most detailed account of the various parables, but Mark 4 includes extensive discussion by Christ on the seed parables.
Jesus compares the Kingdom of God to throwing seeds on the ground. Just as a farmer cannot force his crop to grow, Christian evangelists cannot dictate the time, scope and manner of those who receive the blessings of Christ. We can be faithful in sowing the seeds of faith, but ultimately the fruits are produced by God.
MARK 4: 26-29
26 And he said, So is the kingdom of God, as if a man should cast seed into the ground; 27 And should sleep, and rise night and day, and the seed should spring and grow up, he knoweth not how. 28 For the earth bringeth forth fruit of herself; first the blade, then the ear, after that the full corn in the ear. 29 But when the fruit is brought forth, immediately he putteth in the sickle, because the harvest is come.