@EJh Extremely Snowbank goes back to th early 1894 from Luthur Burbank improving a series of berries starting with crystal white to get one as productive as standard Lawton blackberry of the time. @Shout-rattans Mine Ripen in July.
A good berry is relativly sweet with enough blackberry flavor you know its there. I have not had a berry I would rank more then average but I am good with that for the novelty. Which will be right in time for the 4th of july.
Like @krismoriah I did not have a good experience with snowbank. Each fruit would have very few drupelets, some would have as little as 5-10. Flavor was okay, not great. I had it for a 2-3 years before I decided to remove it. I applied triclopyr to the leaves shortly before dormancy last year, which killed the main plant but still get some small suckers in random places. Easy to tell them apart as they have wicked thorns. It’s possible this does better with another blackberry nearby (I didn’t have one at the time, I have since added Ponca and will add triple crown) or in a warmer climate than mine.