If the iris is in a pot now, then I would leave it until mid-March. If you have dry tubers lyiung around, then get them in the ground now.

I don't think this plant forms a bulb - it grows wild in my garden and when I put it out it's got a shallow, fibrous root system.......

OK, Sid, you may well be correct. We have it but it but I dont remember if it is a tuber or not. I was going on Guest's description.

I would leave it in its pot until your ground is frost free. If it is a bare root plant then pop it in a pot with plenty of room for it to grow. then pot out mid march.

I don't suppose it matters anyway Bulb - I'm just being pedantic lol

Yes I would too.....I have this in my garden...and the berries are still hanging on...also you will have strappy bright green leaves all winter.