Snowdrop Anemone

Anemone sylvestris, the snowdrop windflower, is a spring-flowering perennial from Europe and Asia, twelve to eighteen inches high. Divided, deeply cut basal leaves form a low mound, above which single cup-shaped white flowers an inch and a half across, centred with yellow stamens, open in April. The flowers are lightly fragrant and nod in wind.

It runs at the root and can be genuinely aggressive in loose sandy soil, though it stays comparatively well behaved in clay, which is an unusual case of heavy ground being the safer choice. Where the soil is light, plant it inside a barrier or somewhere the spread is welcome rather than trying to pull it back later.