Summary: With two short parables about seeds that grow and flourish, Jesus describes the reign (kingdom) of God as something that will indeed blossom. It may take time for that to occur, and the outcome may not look magnificent according to conventional standards of power and greatness. The emergence of that new state of affairs is nevertheless definitely going to occur, possibly not what we were expecting, and certain to provide benefits.
I wrote this biblical commentary for those preparing to preach or teach on the passage. Read the commentary at Working Preacher.