Cenolophium denudatum (Seseli libanotis, Baltic parsley): Flat umbels of pretty white flowers in summer. Fine, filigree foliage. Great in borders, sun or part shade. Hardy. To 90cm

Centranthus ruber 'Albus' (White Valerian): White panicles of white flowers in mid-late summer. Very easy, self-seeds. Perennial and hardy. To 60cm.