I think it is after it flowers. I have a veritable rabble of forsythia forming a hedge. I was told by a paid gardener friend that if I cut it back now I will have cut off the growth that flowers.

I'd be interested in the answers from people who no - rather than me lol!

You're right, Pamsco - its after its flowered in spring.

That is what I thought but was checking for a friend as she was saying now it needed pruned.

Thankyou Pamsco and Bamboo

I prune mine as the flowers fade in the late spring, so there is plenty of new growth for the next years show.

That's what the gardeners in Flagstaff, AZ always did.