Gymnaster savatieri

Known as the 'naked aster', Gymnaster savatieri is a herbaceous perennial that single white or very pale blue daisy flowers with yellow centres. It can be hard to track down in the UK but is easy to grow and very useful in the garden as it not only thrives in a sunny spot but also in partial shade, which many perennials don't enjoy. It is very popular with butterflies, and makes a good cut flower.

For good results, grow in any reasonable soil. Deadhead to keep the flowers coming.