In harvest moon tree of tranquility where do u find the seedling.?

I've just been able to pass the bears on Mt. Gelato. Now I'm looking for the seed. I'm not sure where to look, i've tried fishing in the godess spring but I never catch anything. I had just given birth to a baby boy too. And I was wondering by the time he grows up do i have to build all 3 other houses.? And where the last tree is located, for the rainbows.? Thanks, sorry if it's confusing.^