Thank you! Basically, the crops are ammo. The beans are for the rifle, the orange lilies for the rocket launcher and the red blossoms provide health regen. That's what ties farming into combat, you have to plant crops to keep you going.
That little text panel should disappear after 10 seconds, then the controls should be properly visible. Originally I had no explanation at all, that text panel was a last minute addition. Thanks for the kind words!