Hi, yes you're right, those little black things are indeed the seeds from the dahlia's, Derek.

thank you Derek cor blimey my garden will be blooming next year :)

Well it may take more than one year for the plants to grow to flowering size.

Hi, I never thought about them being seed of the other species, I automatically thought bedding dahlia's, I agree it could be several years before large tubers are formed, but there may well be flowers next year, as there are if you take cuttings from overwintered ones, Derek