Agapanthus are excellent plants that provide colour through August and into September with their vivid flowers and attractive seed heads. They have strap-shaped leaves from which straight, slender stems emerge producing a fantastic head of very deep blue flowers. Agapanthus 'Midnight Blue' is shorter than some, reaching around 40cm (16in) tall. They thrive in full sun and enjoy free-draining soil that is moist and fertile. They make great container specimens and actually prefer their roots being restricted in a pot.
Limonium platyphyllum ‘Violetta’ is a summer-flowering perennial with small, purple flowers on branching heads producing a billowing display of colour, particularly when planted in a small group. Its wiry flowering stems look best planted at the front of a border where they can sprawl and soften the edges. Limonium prefers a sunny position, in well-drained soil.
The Honey Bush, or Melianthus major, is a striking, architectural plant that adds great form and texture to the garden. Grown primarily for its attractive foliage, its large leaves are divided into 15 leaflets which have boldly toothed margins and are bright blue-grey in colour. Melianthus stems are hollow and they branch sparingly from the base. Occasionally in summer they produce small brownish-crimson flowers. Melianthus is not completely hardy and may well be frosted during winter, but if cut back hard during the spring it will produce new growth.
Verbena rigida is a short form of verbena that will provide months of summer colour and usually flowers until the first frosts. It produces deep purple flowers on short, straight, narrow stems, reaching around 30cm (12in) tall. The leaves are slender and slightly hairy with wavy margins and this verbena will gradually form a neat clump. It prefers an open, sunny position, in well-drained soil and in colder parts of the country it should be protected with a dry, winter mulch.
Crocosmias add a bright splash of colour to borders during high summer when their vivid flowers open and their attractive, linear leaves also add interesting texture. Crocosmia 'Orangeade' has wiry, branched flowering stems that emerge during August and reach around 120cm (4ft) by the end of the summer. Crocosmias form large clumps and spread by corms on the soil surface. Grow them in an open, sunny position in moisture retentive soil, as they resent soil that dries out in summer.
Lespedeza thunbergii is a slightly unusual, woody based perennial that makes a striking feature in a summer border. It produces long, arching shoots from the base of the plant and in high summer purple-pink flowers are profusely borne in pendent, terminal racemes to 15cm (6in) long. Lespedeza prefers to be grown in a light, well-drained soil in full sun and should be cut back to the base in early spring.