Small-flowered Michaelmas daisy: how to grow, plus the best varieties

It would be hard to imagine autumn without the soft, pastel drifts of the small-flowered Michaelmas daisy (aster). The individual flowers may be small, but they are produced en masse, transforming the plants into cloud-like forms.

While some groups, such as the prolific New York asters, are grown for their striking individual flowers or depth of colour, the small-flowered Michaelmas daisy offers a softer approach with a multitude of flowers, arching sprays and interesting foliage.

Highly drought tolerant and resistant to mildew, and often able to flower in part shade, this distinct group is a welcome addition to the garden.

In the 1900s, this group formed the backbone of what were called starworts or Michaelmas daisies. With the hardy flower revival and the emergence of a more naturalistic style of planting popularised by William Robinson, small-flowered asters started to flourish. But as large gardens declined after the First World War, so did the small-flowered asters. Their resurgence came about thanks in part to the rise of interest in flower arranging in the 1950s and 1960s. The delicate sprays were perfect for autumn arrangements, but it was hard to find them in florists, so enthusiasts started to grow their own.

Fast foward to the recent interest in prairie-style planting, which has revived the naturalist ideal that suits small-flowered asters. Designer Piet Oudolf, a proponent of this style, has used a number of asters in his schemes.

Small-flowered asters are a versatile group, no matter what form your garden takes. This, combined with new breeding, will likely fuel a further rise in popularity.

How to grow small-flowered Michaelmas daisy

Where to grow small-flowered Michaelmas daisy

Small-flowered Michaelmas daisies flourish in good, humus-rich garden soils and will tolerate and even thrive in poorer soils, as long as they do not dry out too much in hot conditions or get waterlogged in winter. Winter drainage is particularly important. In very hot, dry conditions, Symphyotrichum ericoides cultivars such as ‘Blue Star’ are often the toughest. Symphyotrichum cordifolium cultivars and hybrids such as ‘Little Carlow’ enjoy a bit more moisture.

Good light is important for the best flowering, but many such as ‘Chieftain’ or Symphyotrichum lateriflorum will tolerate light, dappled shade – that is, light, dappled shade from deciduous shrubs (not heavy evergreens).

How to propagate Michaelmas daisy

Division is the easiest way to propagate small-flowered asters. Lift clumps every three to five years in spring, removing any old and woody material, and replanting or potting up the divided sections. This will also improve the health and vigour of the plant.

Michaelmas daisy problems

Most species and cultivars of small-flowered Michaelmas daisy show good levels of resistance to powdery mildew, but this does vary. In general, those with rougher foliage are less susceptible to mildew than those with very smooth foliage, but in very hot, dry conditions it can appear on some plants. To reduce the risk, apply a good mulch in the spring to slow down the rate of water loss and divide the plants on a fairly regular basis. Remove any diseased foliage as soon as you see it to prevent spread.

While most small-flowered asters are relatively untroubled by pests, it is worth watching out for slugs in early spring on young, clump-forming plants that are slow to establish, such as ‘Photograph’.

The best small-flowered Michaelmas daisies to grow

Symphyotrichum ‘Little Carlow’

Superb Symphyotrichum cordifolium hybrid with heart-shaped lower foliage. The relatively large 25mm daisies are an intense lavender-blue with yellow centres, held in generous sprays from late September. Will tolerate light shade.

1.2m. AGM. RHS H7, USDA 4a-8b.

Symphyotrichum ‘Prairie Purple’

The hairy, heart-shaped foliage and stems are dark purple, creating the perfect backdrop for the spires of lilac-purple flowerheads (13mm across). Flowering from early autumn, this has one of the longest flowering seasons.

1.3m. RHS H7.

Symphyotrichum lateriflorum ‘Lady in Black’

Arching stems of purple-tinted foliage are interesting throughout the growing season. Tiny (12mm), white flowerheads, with yellow discs that soon turn purple-pink, appear in October. Best in light shade.

1.2m. USDA 4a-8b.

Symphyotrichum ‘Ochtendgloren’

Forms neat clumps of upright stems that hold a mass of starry, purple-pink flowerheads (25mm across) in October. Complemented by strong, straight and narrow foliage. Can struggle over winter if too wet.

1m. AGM. RHS H4.

Symphyotrichum ‘Photograph’

Striking, misty-blue daisies (15mm across) on arching sprays form clouds of colour in autumn. The pale-coloured discs, typically yellow, add to the overall effect and rarely turn purple. Not the most robust of growers.

1m. AGM. RHS H7.

Symphyotrichum ericoides ‘Cinderella’

Upright sprays of tiny, white flowerheads (12mm across) with strikingly prominent, golden discs make this plant a showy addition to the autumn garden. The overall plant is compact and bushy. Will tolerate light shade. 75cm.

Symphyotrichum ericoides ‘Rosy Veil’

Softly arching sprays of creamy-pink daisies (13mm across) on arching stems makes a surprisingly striking show. Flowering from mid-autumn with sufficient gusto to obscure the dainty, heather-like foliage. 90cm.

Symphyotrichum ericoides ‘Blue Star’

A pre-1920s introduction that has stood the test of time. Mid-green, heather-like foliage is a foil for masses of perfect, round, lavender flowers in October. Each flowerhead is 12mm across and they are held on relatively long stems over bushy growth. Prefers well-drained soil.

90cm. AGM*. RHS H7, USDA 3a-9b†.

Buy Symphyotrichum ericoides ‘Blue Star’ from Bressingham Gardens

Symphyotrichum ericoides ‘Pink Cloud’

Bushy growth with fine foliage. Smothered in lilac-pink daisies (13mm across) from mid-autumn. The foliage has an attractive bronze tint in spring that greens during the growing season. Best in a sunny position.

80cm. AGM. RHS H7.

Buy Symphyotrichum ericoides ‘Pink Cloud’ from Langthorns Plantery

Symphyotrichum ericoides var. prostratum ‘Snow Flurry’

The only autumn-flowering daisy to hold its stems at ground level, appearing prostrate. Masses of white daisies (13mm across) in October. Needs a sunny position, but is drought tolerant.

10cm. AGM. RHS H7, USDA 3a-9b.

Buy Symphyotrichum ericoides var. prostratum ‘Snow Flurry’ from Claire Austin

Symphyotrichum cordifolium ‘Chieftain’

Plumes of powder-blue flowers (14mm across) in October over dark-green, heart-shaped foliage. Tolerant of light shade where the soil is moisture retentive.

1.5m. AGM. RHS H7.

Find Symphyotrichum cordifolium 'Chieftain' through the RHS

Symphyotrichum ‘Ringdove’

Daisy flowers (20mm across) of the subtlest lavender, with bold, cream discs. The arching, branched sprays with their dark, narrow foliage create a lovely effect in mid-autumn. Easily grown in an open, sunny position.

1m. AGM. RHS H7.

Buy Symphyotrichum 'Ringdove' from Cotswold Garden Flowers

Symphyotrichum ‘Coombe Fishacre’

Giving away its S. lateriflorum heritage, each flowering stem has numerous side sprays held horizontally. This results in a very dense mass of pink daisies from mid-autumn covering the almost shrub-like plant.

80cm. AGM. RHS H7.