Plant profile: small-flowered asters
With their profuse flowering habit and long season of interest, smallflowered asters are one of the most versatile autumn plants. Collection holder Helen Picton chooses the best
Undemanding and adaptable, these dainty Michaelmas daisies are good news for gardeners and pollinators alike with their profuse flowering habit, long season of interest and versatility
It would be hard to imagine autumn without the soft, pastel drifts of small-flowered asters. 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 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.
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. At this time, the first of the great collections emerged at Aldenham in Hertfordshire, thanks to the Hon. Vicary Gibbs and his head gardener Edwin Beckett, who raised many of the small-flowered hybrids, including the ericoides hybrid Symphyotrichum ‘Hon. Vicary Gibbs’. These were ideal for planting en masse – imagine a huge group of S. cordifolium ‘Chieftain’ weaving its way between autumn-colouring shrubs, its plumes of soft lavenderblue swaying above robust, heart-shaped foliage, or S. ‘Ringdove’, forming a sea of hazy lavender in front of dark, formal, yew hedging. 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 of, for example, the whiteflowered S. ericoides ‘Cinderella’ were perfect for autumn arrangements, but it was hard to find them in florists, so enthusiasts started to grow their own. Soon stunning plants such as the soft-blue S. ‘Photograph’ were growing in ordinary gardens alongside perennials and shrubs.
The 1970s and 1980s brought the realisation that useful plants such as smallflowered asters could have a role in extending the season in new planting schemes. A single plant of the bushy S. ericoides ‘Pink Cloud’, with its delicate, heather-like foliage and pretty, pink flowers, can give a generous display, and a small group or even individual plant of the vibrant cordifolium hybrid S. ‘Little Carlow’ is more than worth the space, providing bright lavender-blue from early autumn. Alpine gardens or raised beds that have lost their vibrancy by autumn can be reawakened with the addition of the unique, prostrate, Beth Chatto introduction, S. ericoides var. prostratum ‘Snow Flurry’. Fulfilling with ease its role in providing a long season of interest, S. lateriflorum ‘Lady in Black’ produces delicious, purple foliage in spring, becoming tinged with green as the dark stems lengthen. In autumn, each arching, bushy stem is covered in tiny, white flowers with purple centres. More subtle, but equally as effective, is the charming ‘Rosy Veil’; as with all S. ericoides, it has dainty, heather-like leaves, but each stem develops a gentle arch before a multitude of pale-pink flowers open in autumn.
The recent interest in prairie-style planting 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, including the striking, purple-pink S. ‘Ochtendgloren’, which, like many with S. pringlei in their parentage, has its origins in the cut-flower trade. Another more modern cultivar that works well is S. ‘Prairie Purple’, whose upright sprays of lilac flowers from early autumn and purple-tinted foliage make a pretty splash. Older, but no less useful, S. ‘Coombe Fishacre’ forms a solid mass of pink, thanks to its stiff, bushy growth and free-flowering nature, which makes a superb contrast with grasses.
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 – and, as we all know, big is not necessarily better.
• Author Helen Picton runs Old Court Nurseries and The Picton Garden with her parents. Her recommendations for the best small-flowered asters can be found over the next five pages.
PLANT PROFILE
What Small-flowered asters are herbaceous, clumpforming 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.
Origins Native to the USA and southern Canada.
Season The main flowering period is from early to mid-autumn.
Size Height varies, from prostrate to 1.5m tall.
Conditions Best in sun or light shade in reasonable garden soil.
Hardiness Most have a hardiness rating of RHS H7, (tolerating temperatures to below –20 º C) and are suitable for gardens in USDA 4a-9b.
*Holds an Award of Garden Merit from the Royal Horticultural Society. Hardiness ratings given where available.