Anemone sylvestris

Simply lovely, and civilised in the garden too. 

Snowdrop Anemone. A charming late spring or early summer bloomer with sporadic flowering beyond, is an ideal ground cover for partially shaded areas. Like a short version of the blooms of the hybrid Japanese anemone, but not a rouge (in white or in pink) going all over the garden and not coming out due to its deep roots. This one smells sweet. Pure white sometimes with a slight pink blush on the back on the petals. This will seed easily for you to make a patch and was to get rid of excess.  An easier plant to grow than A. narcissiflorum, A great plant to plant under Lillies for later interest and to keep the bulbs cool. Or under roses. Great in a meadow or front of your border... 30-40cm. Any soil, anything, but not a desert. 

Massed planting image; Stefan.lefnaer, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons