Salvia azurea var. grandiflora
This is a herbaceous perennial from the South and Central states of the USA. It is a very variable species, with a pure white form which I have not seen. This particular form has larger flowers than the species, but the flowering period in late Summer is equally short. A lax and untidy plant, needing support, the large flowers are an amazing true pale-blue, to be admired during the short flowering-time. Full sun is needed, and with good drainage it will be hardy even in a severe freeze. Propagation can be from cuttings, or occasionally from seed here.