Bohnanza - If no one wants the cards drawn in Step 2, does the active player HAVE to plant them in Step 3?
Yes,

They have to be planted by the active player if not traded to another player.  However,the active player can plant one (ripping out whatever was there) and then, if all his bean fields have no more than one bean planted, plant the second in the same field (ripping out the first bean).

Don't forget that the active player can donate those beans too.  Sometimes it is the best option.