I'm in Zone 5, and blackberries were a bust for me the multiple times I tried them. Floricane types never fruited because I didn't protect the canes over the winter (that's just too much work for me...) and primocane types flowered and set fruit but the fruit didn't ripen before the frost hit.

Never heard of a dwarf blackberry, but it sounds great. lol! I'm in z5 NY and grow Apache thornless. It's a fast-growing MONSTER for me, so I need to prune constantly to keep it in check. I don't cage it -- meaning the rabbits will often strip and kill some canes in winter, and deer come around occasionally and nibble to help keep the plants shorter. :) Our summers can be so wildly different from year to year, but in general, mine ripen in August. This year was an exceptional year for me though and they ripened in July and continued to pump out fruit all through October.

Baby cakes can even be grown in a container.