If it is the green one (the plain species) you will likely be ok to just leave it though as you are not that close to the coast in Herts (the coastal strip is always milder in winter) keep an eye on the weather forecast and only protect if there is severe weather coming.

The coloured forms plus the variegated one are not as hardy and do need some protection.

I have two red/purple leaved ones that I never bother to do anything with - this will be their fourth winter, and they're fine. That said, I agree with fractal that the variegated ones are not so hardy, in particular, the one with pink and green variegation.

I never protect my pink striped Cordyline and Im near the N.E. Coast it has some protection being sheltered from the worst north wids by my garden fence! it hasnt suffered at all.

It's probably because you are near the coast. Even the north sea never drops below 4 degrees in winter so air moving across it stays a little warmer. Five miles further inland and this effect drops off markedly.

Thanks for the answers. Mine is a green cordyline and is already lagged by my over-responsive husband - I'm concerned about the amount and if the poor plant needs to have access to the light and air to function normally!

A few years ago my next door neighbour lost her green one, one frosty night, It was an extremely large Cordy and she was very upset as she had had it for years....Mine on the other hand was much smaller and i tied mine up and it was fine....so it doesnt do any harm to tie it....:>)

I must apologise for my Senior moment Boredra!! I dont have a Cordyline!! mine is a Phormium slightly different, but I think the care is probably about the same they are very much allike arent they? that is why I sometimes mix them up.

Phormiums don't really need protection at all, Maggy7