You need to tell us which plant...

sorry - engage brain before using keyboard.

plant is BERBERIS DAWINNI

Although Berberis Darwinii is a very hardy evergreen variety, I would wait until the spring as by pruning it now you might encourage new, soft growth which will be burnt off with the frost.

My thanks to JIMMYTHEONE for the answer to my question on Berberis.
Graybeard

Thanks BAMBOO for reminding me of basics - like naming the plant concerned.
Graybeard

You can safely trim it back in December or January - it will be dormant then, but I'd wait till spring anyway - that way, you can leave on any parts which are budding up ready to flower.

Thanks Bamboo, I will wait the hedge isn't that bad that I HAVE TO cut it.
regards
Graybeard

ah, you didn't say it was a hedge, I was imagining a free standing individual Berberis - hedges of this plant should be cut once a year, immediately after flowering. With a bit of a tidy up again around July August if you've got lots of sticky out bits...

Hello - totally agree with bamboo, and also suggest you treat it like a pyracantha - regularly cut the leaf shoots out protecting the current flower and future berry for each end of the season, whilst still forming a compact hedge. You may have to go over it two or three times a year, if you choose this option! Berberis can also be left to 'water-fall or fountain' with the new coloured shoots produced in summer for a different effect.