Crown blackberries should be big at planting time just after fruits get into green stage new canes should a pier then again after fruiting ends. Zone 5 pushing limit of time for blackberry plant do its thing I hope you have all sun you funnel in to plants reflective heat would help as in warm place by tin wall on North side plants. If canes flowering now 13 June after 3 to 4 weeks from now July 14th there be change first year all ways slower.

From what others have told me, the reason for that advice is virus transmission (especially from the older black raspberry varieties to other brambles). I seem to see this same advice over and over again. Yet, I've never run across a case where someone has said "My black raspberries got a disease and it traveled to my other cultivated berries". The problem is, that advice usually isn't practical/possible for the homegrowers. I'm not saying that I advise doing it, I'm just saying that after growing berries for the last 4 years (15 beds of 12 varieties of raspberries, 4 varieties of blackberry, plus wild varieties of both) that I haven't had a problem. And that's pretty much the same story I've seen up reported here in this forum. You've already spent the money, and the worst they can do is die. I'd go ahead and plant them. My guess is that you'll be just fine. Good luck! -Glenn

i would find a local grower ... or orchard that grows them...and ask them what cultivar they grow... LOCALLY ... my local orchard even sells plants in spring ... though i love wallyworld ... i would not rely on plants shipped.. in bulk from arkansas ... e.g.: googling : raspberry growers CA ... i found the link below ... getting good cultivars.. really matters for berry production ... pay the money.. to get a good start ... and do not expect much production the first season... and learn all about their biennial tenancies ... and how to prune them ... and do look for EVERBEARING types... they give fruit twice a season ... both of these berries.. are bramble... and can run from horrible ... huge ..... invasive-type plants... that barely berry .... to good acting [blanking on the word i want] .... plants.. that nearly crush themselves with berry production... its really worth it.. to get the right one... ken ps: never met a blackberry that out performed a raspberry .... pps: i have a yellow rasp.. fall gold.. to die for ... and heritage .. same ... i killed off dads historical plants.. years ago.... once i got these .. they grow well in MI ... no clue where you are ... Here is a link that might be useful: link

Native little wild blackberry often has the same 'white dust' on the new growth as the black raspberries. Just because 'all the sites' say a species has a particular characteristic doesn't mean that characteristic is going to definitively separate that species from all others. Species descriptions are maddeningly incomplete. And plants are variable.