>In Pokémon Black and White, if a fateful encounter Shaymin is imported from a Generation IV game, it can get the player a Gracidea from a woman in Lacunosa Town's Pokémon Center.-Bulbepedia
If you've followed those conditions, you should've got those flowers. If you didn't, then it's probably because your Shaymin is hacked.
Hope This Helped :D
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D®.F!@me