I have never been able to overwinter any of the hoops outside near Oerebro
The other small ones may survive a year or two but not for long.
I think the climatic difference between the Iberian peninsula and Sweden is too great.
I suggest pot culture but it is difficult because of the low levels of light here.
Göte.
PS
I, or rather my wife, found an N. assoanus in the gravel of a path.
I have no idea how it got there it must have seeded.