Mike Lyle wrote:
Seabrook said on GQT, 11 Feb this year, to prune _all_ canes of
Autumn Bliss down to the last fruiting shoot in spring (taking off
about a third). They then fruit in June. Then cut right right down
and they fruit again from August...

... from new canes that should have grown new this year.

If you leave lots of last years canes to fruit in June, you might not
force new canes to start growing this year. The plants only have so
much energy to expend.

That's what I would have thought, but Seabrook knows more than I do.
Have you tried it? I assume the whole bed would want feeding, of course.

As I said, I've only ever left a smaller proportion of canes to give
very early rasps, then my normal summer varieties take over. I do get a
wonderful crop from mid/late august to nov from the bliss and allgold.
I'm not jeopodising that :-)