6 Poppy flowers
You need to be careful moving the bulls. You are better making a row horizontally in front of them rather than vertical, as you will find doing it the other way, that you move a bull up or down. You don't want to do that. You just need them to go across.
If you move one across out of the way, then you might be able to make to make a vertical row then to move more than one.
You only need to get them to the other side, once you have done that, gather your crops.
Watch out for those snowballs though as they fall and get in your way!