Jesus told a series of stories designed to enlighten people with what his kingdom is like. He compares magnificent, unknown realities with simple things among us to paint a picture of those unknown realities that we can understand.
One of the common frames of reference was agriculture. In a largely agrarian society, everyone had some exposure. Maybe everyone had some experience.
In one story, he describes responses to the message of the kingdom. Citizens of his kingdom become citizens be choice. His message is an invitation to join his kingdom, to bow to him as king.
In the story, a farmer is planting his field. The seed he is planting becomes a symbol of the invitation message. The planting process of giving the invitation message. And the germination process becomes the person accepting the invitation, becoming a citizen of the kingdom, enjoying the benefits of a citizen and exercising the responsibilities of a citizen.
To be continued.