THESE striking architectural plants are best grown in full sun in dry, gritty soil and are therefore ideal for coastal gardens.

They lift any border, forming basal rosettes of leaves that are often prickly, with attractive silvery-white veins.

From midsummer until early autumn they bear branching stems of round or cone-shaped violet-blue flowers with narrow grey-blue bracts which are good for drying.

Smaller varieties can be grown in rock gardens, while taller ones go well in the herbaceous border, where their skeletal forms can be appreciated throughout winter.

Protect sea hollies from excessive winter wet, especially in cold or exposed gardens. Plants can be divided in spring.

Eryngiums make up a large group of annuals, biennials and deciduous and evergreen perennials. Good varieties include E. x tripartitum, a perennial which grows up to 90cm (3ft), and E. x oliverianum, which has dark green spiny leaf rosettes, blue stems, and flowers from midsummer to early autumn.