Pruning potentilla

There are a few potentillas in the garden where I work, about 4' high. Not sure if they have ever been pruned.....but guess they need a bit of tidying up, once the chance of frosts has disappeared..[not sure when that will be as it is snowing as I type..] How severe do I need to be? Just a couple of inches off all round or go more serious and cut right back to 1'-2'?
Thanks in advance, Lyn

 

they are too big imo, but dont cut them too severely, i think you could go for a re shape

 

I agree, take them back maybe by about a third? The shape is going to be important. But when to do it? Books say March - so maybe a tad later up there? They say to clear out the middle too, and to take it back by half - Imo, though, third off is better.

 

Take 1/3 old wood out of the centre each year for three years, this will encourage new growth from the base. Best time would be April/May or when growth is under way.

Keep the rest lightly trimmed with garden shears after flowering to maintain shape.

Also check any branches that touch the ground, they self layer fairly easily and it's simple to take off a rooted branch for 'free' propagation. Just reduce leght to roughly the size of the rooted portion so you can get a balance between root and leaf. It'll grow away quite happily in any sunny position if you keep it watered during dry spells