About Gladiolus Italicus:
this post is very old, but I am surprised that you consider Gladiolus italicus as little hardyness.
if we look at ancient French flora, it was present even in the north of France (zone 7)
I have a Gladiolus italicus in my garden outside without any protection for 15 years. it comes from a ditch edge of my mother-in-law's house.
it has already withstood -17 ° C and a significant flood in winter for more than 3 weeks (20 cm of water above the earth). shoots appear early in January, but do not fear frost.
this is not the case of the populations of the South? in this case we might think that my Glaieul italicus comes from a relict population of the north?
at home, he likes heavy clay and fresh, almost wet soil. it burrows deeply and is better in the ground than in pots.