Hi, welcome to GoY, as you're growing 'atrovirens' I assume you're growing it as a hedge, in which case it should be trimmed in spring and late summer, Derek.

Derek, Thanks for your reply. Yes, it is a hedge, 16 feet high and a wonderful barrier to the properties behind. Would you consider now to be late summer given how mild the weather is? And what about the tree surgeons trimming when wet? Richard

Hi, I would leave until spring now, we're well into autumn now, and if you were to trim them now, it being so mild, would probably encourage new growth, which wouldn't harden up enough to cope with any heavy frost in winter, I know this weather is confusing, but it could suddenly change, there's no guarantee we'll get another winter as mild as it was this year, so best to be on the safe side and leave until spring, as for trimming when wet, it makes no difference to the plant, only to the person cutting them, they get wet, Derek.

Derek

Many thanks

Richard

Hi Richard, speaking from experience I always cut back, prune my many conifirs in Sept - Oct, this I have done for the past 30 years, I live in the north of England and have never had any frost bite, or other weather related conflicks.
In Autunm tree sap stops rising, giving the tree a winter rest, I personally would not hesitate to prune your Conifirs now, we no longer have the winters of old, your tree's will be just fine.
John.