Stephen wrote:

Focus DIY stores are selling what they call a "black raspberry". Has
anyone heard of these? What are they? What is the difference between a
black raspberry and a blackberry?

One thing that has not been mentioned in this thread, is the difference
in the fruit of black v. rasp-berry. When picking the blackberry the core
of the fruit comes away with the berry parts. In raspberries the core is
usually left on the plant when picked or is easily removed afterwards.

about 10 years ago I grew black raspberries from seed provided by a czech
fruit grower, Jan Kola.

He said it was descended from American black raspberry stock. They had
bluish stems, and had a classic raspberry habit (as opposed to
blackberry). I found the berries uninspiring in taste, and of a firm
texture. They were "blackberry" black in colour. Unfortunately my plants
proved susceptible to disease (I was warned they would be) and I wasn't
inspired enough to preserve seed and try again.

Jan also provided me with purple raspberry seed, of Chinese origin.
They were just like small versions of the "traditional" rasp, but of a
darker hue.

cheers
Jim