Blackberries in Zone 5 or Colder
Is anyone else having success growing blackberries in Zone 5? I've got a Chester that's been fruiting for two years now. Mine has not been vigorous at all -- I get a grand total of about 10-12 berries on the one plant each year, and only one primocane developed for next year so I am expecting more of the same result in future. Perhaps I just need to buy like 5 or 10 more plants, as one just isn't enough!? I find Chester berries are sweet and flavorful IF picked when they are super soft and virtually falling off -- any earlier and they are very tart and not worth eating -- timing is everything.
Based on research it looks like Triple Crown is probably the best choice for me to try besides Chester, and I'll no doubt plant some next spring. However I am also curious if anyone in Zone 5, or colder, has comments on how other hardy varieties such as Darrow and Prime-Jan, maybe others, compare with Chester and TC with respect to flavor and yield. I'd love to try a Boysen but I'd rather not risk it dying at -20 F, as I see they are rated for Zone 6. I am not concerned about thorns, or trailing vs. erect. I am just interested in best flavor and yield of the hardiest varieties. Unfortunately, there just don't seem to be a lot of good options for cold climates. Perhaps I should just plant everything I can find and see what works best here; but if anyone else in Zone 5 or even Zones 3 or 4 has the experience, I'd love to hear about it. Thanks much.