Anemone hupehensis known as windflower or Japanese anemone (don't know why, they are actually from China), find it's place in a shady part of my garden growing in front of the shrubs. They spread here pretty quickly but there is plenty of space in this border and I love to see them flowering in a large number.
In my experience, once established they are pretty difficult to eradicate because they spread by means of fibrous rootstock. But they are pretty flowers and look elegant at every stage of growth. The flowers are long-lasting and flower from August to October when many other flowers has already finished the flowering season.