I don't know what the minimum temperatures for the various species of
Nerine are, but I can tell you that I lost all the winter growing
Nerines I bought from Tony Norris (Nerine Nurseries in England) when
we had two nights going down to 17 degrees Fahrenheit in December 1990.
The temperature did go slightly above freezing the intervening day,
but he Nerines were in pots sitting on the ground, so the soil temperature
was probably the same as the air temperature. In a typical winter here
there will be a few overnight lows of 28F, and the winter growing
cultivars can survive that. "Here" is Livermore, California, USDA
zone 9b.
Kirby Fong
kfong@alumni.caltech.edu