Perry, globe artichokes tolerate a lot of frost, to -10C/14F in my experience and probably lower.
What they don’t do is keep their leaves during a cold winter. Just the roots survive, which power new growth in the spring.
In climates with little winter frost like here, cutting back is not needed. But if it’s likely to be say -8C/18F or lower, cutting back is worthwhile, and straw if beelow perhaps -10C.
