Spec's Garden - I am thinking of a complete change

That's all the wood into the bed, have also topped it off with a lot of the bedding plants, though a good number of them were still in flower its a good time to clear them out and utalie them, never had dahlias flowering as late as this in the past, anyway now covering over with soil, I think I will mound it up to allow for the soil sinking, then leave it over the winter, I still have a number of rudbeckia on display, can anyone tell me if its possible to save seed from them? I have never grown them before but really impressed with the show they have given and still giving, so will definitely go for them again