Acanthus spinosus

From late spring through to midsummer, majestic spikes of white flowers sheltered by purple bracts rise from a bed of prickly, dark green leaves. This clump-forming perennial prefers rich soil and makes a striking architectural plant. Cut stems last well in flower arrangements. Height 5 ft (1.5 m) – Width 24–36 in (60–90 cm)

Aconitum ‘Spark’s Variety’

Upright stems bearing deep violet, hooded flowers, well above the dark green, deeply divided leaves, identify this as one of the monkshoods. The flowers appear from mid- to late summer and perform best in moist, fertile soil, in a woodland garden or border. Taller plants may need staking. All parts are poisonous. Height 4–5 ft (1.2–1.5 m) – Width 18 in (45 cm)

Agastache foeniculum

With its liquorice-scented leaves and spikes of violet-blue flowers from midsummer to early fall, anise hyssop suits a mixed border. For paler-colored flowers, try the cultivar ‘Alabaster’, which has delicate white blooms. Both prefer a sunny site, thriving in rich, fertile soil. Height 3–5 ft (90–150 cm) – Width 12 in (30 cm)

Anemone x hybrida

The Japanese anemone bears semidouble, pink flowers on wiry stems from late summer to mid-fall. The whiteflowered ‘Honorine Jobert’ will shine in any border and like the other Japanese anemones, prefers rich soil. It dislikes cold, wet conditions during winter months. Height 4–5 ft (1.2–1.5 m) – Width indefinite

Asphodeline lutea

The yellow asphodel strikes a dominant pose in the border as its rocket-like spikes of star-shaped flowers stand above other late-spring perennials. Eye-catching blue-green leaves stud the length of each flower stem. Most well-drained soils will suit this clump-forming perennial. Height 5 ft (1.5 m) – Width 12 in (30 cm)

Aster ‘Ochtendgloren’

The long-lasting, purple-pink, daisy-like flowers of this aster are held on branching stems in late summer. It is a stronggrowing plant, producing neat clumps that do not need to be regularly divided. It brightens up borders, can be grown in containers, and is also good for cutting. Height 4 ft (1.2 m) – Width 32 in (80 cm)

Cephalaria gigantea

The giant scabious needs a sizeable border for the best display of its tall flower stems bearing pale yellow, ruffled blooms in summer. Make the most of them by planting at the back of a border against a dark background, such as a conifer hedge or fence, for contrast. Height to 8 ft (2.5 m) – Width 24 in (60 cm)

Cirsium rivulare ‘Atropurpureum’

The deep crimson flowers of this clump-forming perennial, coupled with its prickly green leaves, should make thistles more popular border plants than they are. Suited to damp conditions in a wild garden, they attract insects during the flowering season from early to midsummer. Height 4 ft (1.2 m) – Width 24 in (60 cm)

Crambe cordifolia

Looking like a mass of confetti, the tiny white flowers of this perennial appear suspended in mid-air. The coarseness of the rich green leaves is softened by a cloud of blooms from late spring to midsummer. Crambes are suited to a wild garden and will tolerate coastal conditions. The flowers attract bees. Height to 8 ft (2.5 m) – Width 5 ft (1.5 m)

Cynara cardunculus

Few plants produce such large flowerheads as the cardoon. Fierce-looking bracts sit below brush-like flowerheads of blue-purple florets to create a dazzling summer and early fall display. Protect plants from strong winds and in cold areas, mulch around the plant base. Height 5 ft (1.5 m) – Width 4 ft (1.2 m)

Delphinium Blue Fountains Group

This hardy delphinium is the ideal choice for a windy garden as the plant is compact; the flowers grow to just 32 in (80 cm) high and do not need staking. Early summer blooms appear in short spikes in a variety of shades of blue, mauve-blue, and white. Suited to a cottage garden or mixed border. Height 32–39 in (80–100 cm) – Width 24 in (60 cm)

Delphinium Pacific Hybrids

A cottage garden favorite, this tall perennial comes in a range of colors, including blue, pink, white, and violet. After the midsummer flowering, cut back the stems to encourage another flush of double flowers in late summer and early fall. Protect from strong winds. Height 4–6½ ft (1.2–2 m) – Width 36 in (90 cm)

Dierama pulcherrimum

The delightful name of angel’s fishing rod perfectly suits this elegant perennial whose pendent, pink bells move gracefully in the slightest breeze against narrow, grass-like, green leaves. This combination looks good in the middle of a border or as edging alongside a pathway. Height 3–5 ft (1–1.5 m) – Width 24 in (60 cm)

Helianthus ‘Lemon Queen’

Sunflowers are always a good choice for the back of a border and this variety is no exception. Pale yellow flowers with a slightly darker eye mark this out as one of the more subtly colored choices. Expect a long-lasting display from late summer to mid-fall. Height 5½ ft (1.7m) – Width 4 ft (1.2 m)

Helianthus ‘Monarch’

The almost spidery blooms of this sunflower make it stand out from the usual crowd. Predominantly yellow with a pale brown eye, the semidouble flowers appear from early to mid-fall. Long, hot summer months will promote a beautiful flowering display. Height to 6 ft (2 m) – Width 4 ft (1.2 m)

Inula magnifica

This fast-growing, clump-forming plant needs plenty of space in the garden. Large, frilly-petalled flowers are formed, up to 20 at a time, in late summer above a foil of dark green leaves with softly hairy undersides. Ideal for a wild garden, the plant likes sun but will tolerate damp soil. Height to 6 ft (1.8 m) – Width 3 ft (1 m)

Leucanthemella serotina

This large-flowered daisy makes excellent cutting material, lasting well in the vase. It is a vigorous plant, with stout stems that should not need staking, and prefers a moist situation with full sun or partial shade. It is useful for illuminating darker areas of the yard. Height to 5 ft (1.5 m) – Width 36 in (90 cm)

Leucanthemum x superbum ‘Wirral Supreme’

One of the Shasta daisies, ‘Wirral Supreme’ boasts fully double flowerheads of white petals with pale yellow eyes. These are formed from early summer until early fall, providing a long-lasting display. A strong growing plant, it needs moderately fertile soil and sunshine to perform well. Height to 36 in (90 cm) – Width 30 in (75 cm)

Macleaya microcarpa ‘Kelway’s Coral Plume’

This pink-flowered plume poppy is at its peak in early and midsummer, when large, open floral sprays sit above a sea of gray-green leaves. A tall, showy plant, it is best sited on its own, forming an eye-catching screen, or at the back of a large mixed border. Macleayas can be invasive. Height to 7 ft (2.2 m) – Width 3 ft (1 m) or more

Phormium tenax Purpureum Group

Long, fibrous, sword-shaped leaves burst forth from the base of the New Zealand flax. The red-purple foliage contrasts well with paler phormiums or grasses. Alternatively, use it on its own to dominate a border. The plant Iikes fertile soil in full sun; mulch the base in winter in frost-prone areas. Height 8–9 ft (2.5–2.8 m) – Width 3 ft (1 m)

Romneya coulteri ‘White Cloud’

This plant will eventually become a woody perennial once it becomes established. Large white petals with a bobble of yellow stamens in the center create a winning display. Protect plants from cold, strong winds, and in frost-prone areas, choose a site against a warm wall. Height 3–8 ft (1–2.5 m) –Width indefinite

Salvia uliginosa

Native to South America, the bog sage comes into its own from late summer to mid-fall, when square stems bearing clear blue flowers emerge above mid-green, toothed leaves. As the name suggests, bog sage is a moisture-loving plant. It is tall and suited to the back of a sunny border. Height to 6 ft (2 m) – Width 36 in (90 cm)

Thalictrum flavum subsp. glaucum

The yellow meadow rue is a clump-forming perennial that spreads by means of underground stems or rhizomes. Its blue-green foliage is offset by the pale sulphur-yellow flowers formed in summer. The variety ‘Illuminator’ is taller than the subspecies and has bright green leaves. Height to 3 ft (1 m) – Width 24 in (60 cm)

Verbascum ‘Cotswold Queen’

Synonymous with cottage gardens, this semievergreen perennial will brighten any summer border with its prominent spikes of yellow, saucer-shaped flowers. In a garden exposed to the elements, this tall plant will probably need staking. Many Verbascum species are short-lived. Height 4 ft (1.2 m) – Width 12 in (30 cm)

Verbena bonariensis

A popular plant, this verbena comes into its own when grown with grasses, allowing its branched flowerheads to punctuate a border display. It can be grown at the back of beds, but its slim stems also look striking at the front. It flowers from midsummer to early fall. Height to 6 ft (2 m) – Width 18 in (45 cm)

Veronicastrum virginicum

From summer to fall, the dainty flower spikes of this perennial bring white, pink, and purple shades to border plantings. For a pure white-flowered variety, look for V. virginicum ‘Album’ and grow it with dark foliage plants to bring out its best attributes. Height to 6 ft (2 m) – Width 18 in (45 cm)