It would be hard to imagine autumn without the soft, pastel drifts of small-flowered asters. The individual flowers of asters 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 asters offer a softer approach with their 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.
Small-flowered asters are herbaceous, clump-forming perennial members of the Asteraceae family. They are drawn from five species, all part of the largely American genus Symphyotrichum, (previously Aster). They are distinguished through their flower size and profusion of blooms, along with their bushy habit.
Flowers are 12mm to 25mm across, nearly all with only one row of ‘petals’, and carried in generous sprays. Foliage varies, from narrow, lance-shaped to broad, heart-shaped leaves and they are native to the USA and southern Canada.
- Season The main flowering period is from early to mid-autumn.
- Conditions Best in sun or light shade in reasonable garden soil.
- Hardiness Most have a hardiness rating of RHS H7, (tolerating temperatures to below –20ºC) and are suitable for gardens in USDA 4a-9b.
Symphyotrichum ‘Little Carlow’
Superb S. 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.
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.
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.
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.
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†.
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.
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.
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.
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.
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.
Small-flowered asters 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 to those plants with S. pringlei in their heritage such as ‘Ochtendgloren’, which, in suitable conditions, will be hardy below -10ºC.
Good light is important for the best flowering, but many such as ‘Chieftain’ or S. lateriflorum will tolerate partial shade – that is, light, dappled shade from deciduous shrubs (not heavy evergreens).
In very hot, dry conditions, S. ericoides cultivars such as ‘Blue Star’ are often the toughest. S. cordifolium cultivars and hybrids such as ‘Little Carlow’ enjoy a bit more moisture. Most species and cultivars show good levels of resistance to powdery mildew, but this does vary.
Where to see and buy
- Larch Cottage Nurseries Melkinthorpe, Penrith, Cumbria CA10 2DR
- Norwell Nurseries Woodhouse Road, Norwell, Newark, Nottinghamshire NG23 6JX
- Old Court Nurseries Walwyn Road, Colwall, Malvern, Worcestershire WR13 6QE
- Sussex Prairie Garden Morlands Farm, Wheatsheaf Road, West Sussex BN5 9AT
- Upton House and Gardens Nr Banbury, Warwickshire OX15 6HT
Author Helen Picton runs Old Court Nurseries and The Picton Garden with her parents. Old Court Nurseries and The Picton Garden in Worcestershire is home to the National Collection of autumn-flowering asters and related genera.
Helen Picton is the third generation of Pictons to work in nursery, which currently boasts more than 400 forms. Open from May to late October and for the NGS.