Macleaya cordata (Plume Poppy)
Full sun or partial shade. Giant background plant with large, blue-green leaves, topped by cream-coloured, airy plumes. (2m - 6') Blooms July and August. Full sun/part shade. Can be aggressive.
Nepeta x 'Dropmore Blue' (Catmint)
The dense gray-green foliage is tolerant of heat and humidity. Masses of blue flowers reach 30 cm (12") and continue from June to September. Good lavender substitute.
Perovskia atriplicifolia (Russian Sage)
Fine-textured, gray-green foliage. Flower spikes of lavender blue. Contrasts beautifully with coarse-textured plants. Former Perennial Plant of the Year. Blooms July to September. A new, shorter cultivar, called 'Little Spire', was introduced last year and has less tendency to flop. The species grows to 1.5 m. Doesn't like wet feet in winter.
Persicaria polymorpha (Fleeceflower or White Dragon)
Persicarias have a reputation for being very invasive. This one doesn't run, it clumps. It is a tall, stately plant with plumy, astilbe-like, creamy white blooms. It likes a rich, moist soil and full sun or light shade. Grows to about 200 cm 5' tall. Zone 3.
Phlox paniculata cultivars (Garden Phlox)
Growing to about 1.2 metres (4 feet) tall, fragrant garden phlox is a mainstay of the late summer garden. Many cultivars are available, in colours ranging from shades of pink, to white, to red, to orange, to mauve-blue, to lilac and more. Deadhead to promote flowers, grow in well-drained soil in full sun. Prone to powdery mildew (try to ensure good air circulation) but pure white cultivar 'David', the 2002 Perennial Plant of the Year, is much more resistant than most.
Physostegia virginiana cultivars (Obedient Plant, False dragonhead)
A fun plant that has a tendency to encroach on other plants if not contained. Several cultivars with white, pink and variegated leaves add to the diversity of this plant. (To 1.2 m - 4'). Called "Obedient Plant" because the flowers on the upright spikes can be moved and stay obediently in the position in which they are put. Full sun to partial shade. To 60 cm tall. Blooms July through September. New cultivar 'Miss Manners' promises to be less invasive than older types.
Rudbeckia cultivars (include fulgida var. 'deamii', 'Goldsturm' and 'Herbstonne').
Black-eyed Susan and others. Attract butterflies and bees. 'Herbstonne' also attracts finches and grows to 2 m (7') tall. Very long blooming period. Zone 3.
Rudbeckia hirta (Gloriosa daisy)
Offers a glorious display of blooms from July to frost. Lots of cultivars to choose from. Colours include yellow, orange, bronze and mahogany. Attracts bees and butterflies. Zone 5, often treated as self-seeding biennial.
Scabiosa columbaria 'Butterfly Blue' (Pincushion Flower)
Hardy to zone 3, this plant really blooms all season long (June to September) with masses of lavender blue, round, pincushion-like flowers. (40 cm - 16"). Full sun. Attracts butterflies. Perennial plant of the year in 2000. Zone 4.
Solidago rugosa 'Fireworks' (Goldenrod)
A clump-forming perennial that has horizontal branches of golden yellow flowers that look like exploding fireworks. Blooms from late August to October. Zone 5.
X Solidaster luteus 'Lemore'
A inter-genera hybrid between Aster and Solidago (goldenrod). The soft, primrose-yellow blooms are shaped like a small daisy flower but held in a goldenrod arrangement which is showy from August to October. Can be prone to powdery mildew. (To 80 cm - 32"). Zone 5.
Various cultivars, most with yellow flowers, but white, pink and blue flowered cultivars exist. Common mullein grows to 6 feet tall. Tall, architectural plants with silvery-white to grey-green foliage. Prefers poor, well-drained soil in full sun. Tolerates drought. Watch for mildew and caterpillars. Some cultivars hardy to Zone 3.
Veronica longifolia cultivars (Speedwell)
Upright perennial grows to 1.2 metres (4') tall. Pointy, toothed, mid-green leaves; tubular, 5-lobed, lilac-blue flowers in late summer to early autumn. Like all veronicas, a very useful plant. Zone 4.
Veronicastrum virginicum (Culver's Root)
A native North American wildflower that grows in full sun. Spikes of white (or sometimes pink or bluish-purple) flowers bloom from August through September on 1.5-m (5') plants. Needs rich, moist soil to grow well. Zone 3.