I love the drama of big spiky plants. As the summer moves to its later stages, the many garden plants that have a thistly habit reach their peak, and their jagged outlines and often grey-silvery colouring are a good antidote to the mounds and cushions of more vibrantly coloured perennials.
Some varieties are perennial - the globe thistles (Echinops), artichokes (Cynara) and bear's breeches (Acanthus) are among these, but some of the most eye-catching are biennials which, having spent a year looking decidedly underwhelming suddenly sprout into amazing Gothic candelabra. The Scotch Thistle (Onopordum acanthium) is one such - eight feet tall, with felted white leaves in huge sheaves around its winged stem, it branches wildly to bear tomato-sized thistle heads of blue-purple. It is invaluable as an accent in larger schemes, but give it room - the leaves make uncomfortable close-quarters partners in small spaces. Once you plant it you have it forever - it self-seeds like crazy.
One family of garden-worthy plants has a wide range of forms that run from something the size of the Onopordum down to much less threatening two-footers. The eryngiums, or sea hollies do have some perennials among their number, such as the stately E.pandanifolium (widely branched flower stalks to about seven feet, with, in the dark Chelsea Physic Garden form, rusty claret buttons at the ends) - the most elaborately formed flowers belong, however, to the biennial Eryngium giganteum, commonly known as Miss Wilmott's Ghost.
Green in bud, the whole plant reaches its peak in a blaze of silver, the extravagantly jagged ruff to each flower veined with pale buff as it dries. The blue flowers are loved by insects, including wasps, and once they are over the plant decays beautifully, holding its structure throughout the winter, the deeply cut and thorny flower heads never better than when frosted on a sunny morning. The story goes that the Edwardian plantswoman and gardener Ellen Wilmott surreptitiously introduced this, her favourite plant, to other gardens by sprinkling the seed as she visited. Like the Onopordum it is a vigorous self-seeder, favouring hot situations and gravelly soil. Besides the species, there is a selected form with even more flamboyant costume, E.g. 'Silver Ghost', but either plant will reward you with a glamorous late-summer display to set against daylilies and grasses, with which they associate particularly well.Paul Ridley Design