Yes Gorgi, I'm sure. That is, I'm sure about the information we recovered in our research.
LaRadek Is listed by a few European growers as having survived a winter in the Czech Republic to minus 18 degrees Fahrenheit. The American mother tree of Marseilles Black VS, is in Columbia, Maryland. The weather station there listed a winter low there of between 18-19 degrees below, Fahrenheit, two to three years before Warren shared cuttings with Herman, and Warren lives in Columbia, Maryland. As to Hanc's English Brown Turkey, Miller's Nursery had it listed as being able to grow into zone 4b, with winter protection., when they were selling it. (They have since lost the variant that they sold to Hanc.
The rest, such as Danny's Delight originated in a zone 6a/5b part of Michigan. Or the originators/finders classify it as cold hardy for them. Hardy Hartford has been growing in Hartford for over thirty years without winter protection. Although it is planted were it is protected from winter winds. Hartford is a zone 6b. I don't think Hardy Hartford is a cold hardy enough for our zone 5, without some sort of winter protection, from the wind.
As an experienced fig grower your self, you know that cold winter hardiness is conditional. The figs age before it is exposed to the cold? Whether the it is grown in dry spot or wet spot. Was it allowed to reach maturity before being left exposed to winter cold. Was the new growth, and number of fruits controlled before winter set in.
Although all of the figs being tested by us are considered winter hardy, to a certain point, they cannot be grown like a newly planted apple or pear tree, and left on their own. We had nothing but failure after failure when we first tried to grow figs here. It took a lot or reading, research, talking to other fig growers, before we started getting figs not to die to the ground, and fruit for us.
So, I don't think any one who does not understand that a fig is a fig, and not an apple or pear tree, will not be able to grow figs in a cold winter area of the country. Even so called cold hardy figs are still figs. They do not become hardy until the are mature. (Three to seven years)? They do not like winter wind. They do not like cold wet ground. Their growth has to be controlled. There crops have to be controlled.
I don't suggest even cold hardy figs to the casual grower.If your not willing to learn what the fig needs, and willing to look after it. Then one should not waste ones money.
I hope that clarifies better the label. "Cold Hardy", and what we are doing here
Bob, zone 5 Connecticut