Sweet! Thanks a lot! I seem to get tons of white and red f's, but never got an swf block. Now I can look what happens if I get all three of them! (I did put my spare blocks there as well.)
@Niks from nibbling pigges. Never really knew what to do with them. Then I started seeing loads of forums posts asking to trade different ones. Today I realised I had about 36 of them.... Might as well help some people out :).
I've got the odd white F and red one by petting trees. I think the red fs are more common to get with the top croppery and soil skills.