Sam,
One of my most respected college professors warned me against making
all-inclusive statements"
You said, "It's important to remember that blackberries are hardy in Zone 3
only if
they are protected by adequate snowcover. While enduring accumulations
of snow are common in Minnesota, they are less so in the Great Plains
states like Nebraska due to periodic warm spells in winter. -- Sam
Brungardt, St. Paul, Minn. (USDA Zone 4b)"
Your statement would be true had you added the word, "some." Here in
zone 3, SOME of my blackberry varieties need snow cover and SOME do quite
nicely without it. A couple of years ago, I received no snow at all and
most of my blackberries produced normally.