You cannot get that item in Pokemon Black.
If you mean the gracedia flower, you can't. The only way was to win it in an online event. The winners received the flower. Sorry
If this is in Diamond or Pearl, it is impossible to receive the Gracedia flower or Shaymin Sky Form. In Platinum, you must have a Shaymin IN YOUR PARTY and then ask the girl. She should give you the Gracedia flower, but it does not work at night or on any other Pokemon.
You cannot get the gracedia flower in Pokemon pearl. Rather, you must obtain Pokemon platinum and trade your shaymin there. You talk to a lady on the road in Floaroma town and she will give you the flower. Hope this helps.
If you have Shamin in your party go to floaroma town and in the middle of the town there is a girl talk to her and she gives it to you.
Yeah there is but it's not with me right now. Go to neonseeker/games/actionreplay.com
I tried it, and it didn't work.
u beat the elite 4 5 times
to get the flower you have to transfer a shaymin from D/P
get a gracedia flower and have shaymin hold it during day only (if you are on pkmn diamond or pearl you will have to get a friend to trade a Pokemon holding it from pkmn platinum)(if you are on pkmn platinum a girl in the flower shop in floaroama city)
shaymin needs to have a gracedia flower to change into sky forme but it will return to land form when it is dark or if it comes into contact with ice, im not sure if it can change formes on Pokemon pearl though
by talking to a certain person while having an event shaymin in ur party
You get the Gracedia Flower from the Blonde girl in Floaroma Town if you are playing Pokémon Platinum (not Diamond or Pearl) and have a Shaymin in your party (the Shaymin event has been for USA and UK) after you get the Gracedia it will go in to your key items, use it on Shaymin and it will change into it's Sky Forme!