A close-up of the many flowers of Rudbeckia ‘Herbstsonne’
If you look up this plant via a search engine, you’ll find there are at least three names bandied about for it: Rudbeckia laciniata ‘Herbstsonne’, Rudbeckia nitida ‘Herbstsonne’, and the one I’ve used, Rudbeckia ‘Herbstsonne’. From what I’ve been able to determine so far, this plant is purported to be a cross between Rudbeckia laciniata and Rudbeckia nitida, so neither of the first two names can be valid, as they imply that only one species is in the genetic background of the cultivar. I’m still trying to verify that it is indeed a cross, though.
In any case, ‘Herbstsonne’ coneflower is a relative of the commonly-known black-eyed susan. Missouri Botanical Garden’s Gardening Help has a small article on Rudbeckia. BBC Gardening also has some information about Rudbeckia ‘Herbstsonne’ from a gardening perspective.
Botany Resource Link: What is a Cultivar? via the Australian Cultivar Registration Authority.