Those onions sound interesting. How hardy are they?
Extremely hardy.
They are coming up now, despite hitting zero last week; and have survived winters with lows of -15 to -20 for 2 or 3 weeks straight, highs never getting above zero.
They also get temps of 95-105 for 3 or 4 weeks in the summer, and will often, though not always, go dormant then; but come right back with water when it cools down a bit.