To Prune or Not?

To Prune or Not?

I planted some Blue Prince and Blue Princess holly bushes last fall to create a hedge along one property line. My question is: should I prune them now or wait? I'm in Zone 5. My intent is to cut back the top growth to encourage better 'filling in.' Any suggestions/tips would be greatly appreciated!
Yams – the breakfast of champions

Yams – the breakfast of champions

Narcissus

Narcissus

Salvia!

Salvia!

my new room

my new room

Fall and photos

Fall and photos

The bishop

The bishop