What kind of flower is this?
I think it is Anemone hupehensis. We have this species in our garden, and the seeds and dead leaves look very similar to the ones in your picture. The leaves are large,jagged and palmate and they have beautiful flowers in the summer/autumn (I've seen red, pink and white). The fruits/seeds also look very distinctive and cotton-like. The species is originally from Asia/China.

Here is a picture of the fruits/seeds:

(Hard to find good ones, this from Instagram page http://www.ipopam.com/tag/höstanemoner)