Hopefully, Flora will reply, as she's more familiar with your climate. I'm making a couple of assumptions--it's an outdoor plant, and wet means that it won't be freezing.

If it's not in danger of freezing the cut tips, it is safe to take tip cuttings off a young plant--just keep in mind that it's a slow grower. It may even encourage further bushing and growth. If it's about a foot overall, you could take 3-4 inch (sorry, I stink at conversions) sprigs. I do harvest mine carefully throughout winter, but it's inside as it wouldn't survive winter outside here.

No we have frost too.
I hope floral_UK does too. It's for a roast. I'd rather fresh. So I thought to check as it's a (I'll say) sub-tropical plant.
I thought I read it was a slow grower. Fantastic flowers though! Love Blue!!

Thank you though.

Harvest it any time you like, mushibu10. Although, if it is only a foot tall, you don't want to take too much yet. Even if it is freezing you won't harm it. Freezes here are not long and not deep. Rosemary will not turn a hair. I pull off entire branches all year round.

Rosemary isn't sub tropical. It is Mediterranean and gets frosts in its native habitat.