It it half tender could it have got caught by a late frost?
Also it likes dry conditions and it was very wet most of this summer?

Hi.I am the breeder of Black Pearl and in order to maximise flower production the plant requires a thoroughly good ripening.The recent wet Summers are working against the ripening process so a change of position may help but certainly as the plants become older more flowers will be produced.Suggest also trying the cultivar Red Dragon as it is very floriferous under adverse conditions.As a footnote Black Pearl has survived -11 degrees with little damage and will tolerate dense shade to full Sun.

Ok, thanks everyone! I'll change the position and see how that works.
To Steveyandall: what is a thoroughly good ripening mean?