Here you will find a list of all the seed powers TumbleSeed can take on. Each seed must be planted in a plot to activate. Sometimes, you can find plots with seeds already planted in them which require stepping on them to activate.
Any seeds besides the starting seeds can be found in the Vineguard Shrines throughout the levels, in shops, at the end of the bounce minigame, or occasionally already planted in soil patches throughout the world. If you already have a seed in your inventory that the game tries to spawn, a heart will spawn instead of a duplicate seed.
List of Seeds