When i use the sicle on a flower it breaks dirt blocks on the same level

I can confirm this behaviour, with grass blocks, not dirt.

It's because BlockGrass implements IGrowable
which means isPlantType() returns true
I assume grass is not supposed to be harvested, in which case a simple

 && !b.isInstanceOf[BlockGrass]

in items.scala:302 will fix the issue.

Fixed via a5df88b