Potentilla Hedge Q'

Hi people, I have a long Potentilla hedge which is quite deep & high. I have read it can be cut back hard to just above ground level. Now, before I take to it with the shears, I just want to confirm this & how hard are we talking. I don't want to cut it so hard it wont grow back.
Mamny thanks

 

Thats a common hedge here. I'm not sure if its the same in the UK, but here we would cut them down to about 20cm in what we call "Spring Winter." That is, the period when winter is turning into Spring. In my opinion, and others may disagree, its also a good idea to put bark around the roots afterwards. We do that here because the roots dont seem to like hot summer temperatures, and bark has the ability to keep the ground cooler.

 

Many thanks I'll do that, just seems very brutal to cut so much off..