when do you prune Mahonia japonica?

Mahonia japonica like all shrubs after the flowering April May if you cut now you won't get flowers

Too late to prune now although it wont harm the plant. Its very tough. Best after flowering. Rod

To get the best of both worlds, I would prune it just as the flowers are fading next spring. Mahonias are tough plants so you won't harm it. Cut to immediately above a leaf joint (or even cut branches out completely if you need to reduce the spread). I did this to mine about three years ago and it carried on as if nothing had hapened.