Can't open world without it crashing immediately! Please help :(

I went to fill in some land with pink tulips, and something went terribly, terribly wrong. I think its trying to fill every block in the universe with pink tulips now! I was having such a great time with this world and I can no longer open it without everything crashing Please fix! And is it possible to get everything back to normal? I've spent days on this world and put in a lot of hours and I don't want everything to be destroyed!!!