It is a native of Uruguay and E. Argentina where an occasional -12 C (10.4F) frost sometimes occur. Reliable information reports 'Alberto Castillo' having survived impervious -24 C (-11.2 F) temperatures in the States. Of course it is not what it would prefer coming from a sunny part of the world with mostly mild winters. Not at all what one would expect. So why is it hardy? 1. Facing extinction in its native Greenland, Vikings dug up all the remaining bulbs and sailed to the Rio de la Plata and planted the bulbs, long before the Portuguese arrived in the 16th century. (That would explain the hardiness.) OR 2. Habitat is not an indication of hardiness. There are other evolutionary factors at work. Bob Nold Denver, Colorado