Asters and Michaelmas-daisies
What are they?
The asters are members of the daisy family - the Asteraceae. At one time, the majority of these plants were grouped together in the genus Aster, but more recent research has shown that they are not all close relatives and many species are now found in a number of other genera. The North American members of the family include the plants that are grown in UK gardens as 'Michaelmas-daisies' and are now in the genus Symphyotrichum. In the species below, I prefer to use the botanical names for these species as used in their native North America and I have only used gardening names for the hybrid forms which arose in cultivation in the UK. Alternative 'garden' names for the North American asters are given in parentheses.
Where are they found?
Our one native species in this group can be found in coastal saltmarsh and shingle banks. Other species are of garden origin and occur occasionally on rough ground and roadsides, where they can persist for a long time and spread to form quite extensive colonies.
Identification
Our native Sea Aster is straightforward to identify by its habitat choice and its fleshy leaves. The North American asters are notoriously difficult and many may be unidentifiable, since their parentage is often unknown and may even include some hybrid combinations that have not formally been described. I have here taken identification of East Anglian plants as listed in the local floras in good faith, while those I have found myself have been identified based on key characters supplied in the standard British floras, but no doubt there is still much to learn about these plants and identifications may be reassessed in the future. When faced with any North American aster (Michaelmas-daisy), details should be taken of leaves (length and colour), phyllaries (whether broad or narrow and whether tightly pressed or curved outward), stem hairs and flower colour. The latter is often variable and not useful without information on other features. When looking at the leaves, it is worth checking whether they narrow neatly into the stem at the base, or whether they end more abruptly, resulting in a rather wide base - the latter is referred to below as 'auricled' which means resembling ears or lobes.
Sea Aster Tripolium pannonicum
Native. Widespread and abundant in coastal saltmarsh habitats and occasionally in coastal shingle. Flowers July to October. Leaves thick and fleshy. Most plants have pale lilac petals but these can be absent in some plants (usually called the 'rayless' form), leaving just the central cluster of yellow florets.
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Common Michaelmas-daisy Symphyotrichum x salignum
A non-native plant that originated as a hybrid in cultivation with Lance-leaved and New York Asters as its parents. Possibly the most frequent aster in East Anglia. Flowers September to November. Stems hairless below, lightly hairy towards the top of the plant. Leaves 2-10cm long, typically pale green, lighter beneath; relatively narrow, margins entire or with a few small teeth; bases slightly auricled. Petals pale bluish-lilac, or starting white and becoming bluish-lilac with age. Phyllaries narrow, clearly pale-edged, mostly pressed to the flowerhead with some of the basal ones curved outward a little.
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Late Michaelmas-daisy Symphyotrichum x versicolor
A non-native plant that originated as a hybrid in cultivation with Smooth and New York Asters as its parents. Recorded at a handful of locations throughout our region. Flowers October to November. Stems more or less hairless. Leaves 2-15cm long, typically deep green, lighter beneath; relatively broad, margins entire or with a few small teeth; bases slightly auricled. Petals pale mauve or bluish. Phyllaries narrowly pale-edged, mostly pressed to the flowerhead with free tips, hairless.
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Lance-leaved Aster Symphyotrichum lanceolatum
(Narrow-leaved Michaelmas-daisy) A non-native plant occasionally found in rough, grassy areas as an escape from cultivation or garden throw-out. Flowers September to November. Stems hairless below, lightly hairy towards the top of the plant. Leaves 2-15cm long, typically pale green, lighter beneath; narrow, margins entire or with a few small teeth; bases tapered gradually to the stem. Petals usually white. Phyllaries narrow, clearly pale-edged, pressed to the flowerhead and only free at the tips. Some plants have lightly bluish flowers, but this might suggest that they are actually back-crossed hybrids rather than true Lance-leaved Aster.
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New York Aster Symphyotrichum novi-belgii
(Confused Michaelmas-daisy) A non-native plant occasionally found in rough, grassy areas as an escape from cultivation or garden throw-out. Flowers September to November. Stems typically hairless towards the base and with a few hairs along the ridges higher up. Leaves 1-12cm long, typically deep green, lighter beneath; relatively broad, margins entire or with a few small teeth; bases clearly auricled. Petals pale mauve or bluish in the true species but may be white to purple in cultivated forms. Phyllaries mostly green, the inner ones with pale bases; clearly curved outwards, hairless.
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New England Aster Symphyotrichum novi-angliae
(Hairy Michaelmas-daisy) A non-native plant grown in cultivation but only rarely recorded as an escape or garden throw-out. Flowers September to October. Stems clearly hairy. Leaves 2-12cm long, typically rich green, lighter beneath; relatively broad, margins entire or with a few small teeth; bases strongly auricled and clasping the stem. Petals may be white or pink to purple or bluish in cultivated forms. Phyllaries narrow, strongly curved outwards, even in bud; hairy.
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China Aster Callistephus chinensis
Introduced from China as a garden ornamental and grown in a wide range of colours. Recorded on a handful of occasions as escapes from cultivation or surviving for a short time where discarded. Flowers July to September. A small, branching, annual plant, growing to around 40cm in height. Flowers very variable in colour and in number of petals, included many-petalled, 'mophead' types. Phyllaries prominently spreading and broad-tipped.
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