Actualy the only seed you can put on an empty pot are ice flower seeds, and you always get the Ice flower as final plant. The other ones you get by exchange 5 seeds by an flower pot.
About the chances there are not info about it, but the ones I have calculated from the ones I had are like 65% grown lizard tongue plant, 15% dryad's heard flower, 10% midnight bloom flower, 5% grown ember flower, and low low chances of fairy dancer and finger snapper.