Seeing as this is actually an original PlayStation game I've moved it to the right section.
This seed can only be had via an extra mission you can unlock using a game save from the original Tomba! game that had you finish certain missions in that game. In this case you had to complete the "Lost Dwarf Child" mission in the original. You could then load that save into the Tomba! 2 game to unlock the mission to get the seed.