I believe there have been attempts at putting that vegeation in other regions apart from Velen/Novigrad but it does not appear possible for whatever reason.
I am not surprised then. I found curious than no one else wanted this grass in those area. Too bad. But hey new things are found everyday. Maybe it will come^^
It's not possible unfortunately. I spent a good week or two trying to get it to work in other regions but all I could accomplish was corrupted looking grass.