Symphyotrichum novi-belgii
(New York aster)

Pictures

Picture	Title	Caption	Copyright
Title Habit Caption Symphyotrichum novi-belgii (New York aster); flowering habit. Thane Biodiversity Park, Thane, Maharashtra, India. April 2018. Copyright ©Dinesh Valke/via wikipedia - CC BY-SA 2.0	Habit	Symphyotrichum novi-belgii (New York aster); flowering habit. Thane Biodiversity Park, Thane, Maharashtra, India. April 2018.	©Dinesh Valke/via wikipedia - CC BY-SA 2.0
Title Habit Caption Symphyotrichum novi-belgii (New York aster); flowering habit. Thane Biodiversity Park, Thane, Maharashtra, India. April 2018. Copyright ©Dinesh Valke/via wikipedia - CC BY-SA 2.0	Habit	Symphyotrichum novi-belgii (New York aster); flowering habit. Thane Biodiversity Park, Thane, Maharashtra, India. April 2018.	©Dinesh Valke/via wikipedia - CC BY-SA 2.0
Title Habit Caption Symphyotrichum novi-belgii (New York aster); flowering habit. Thane Biodiversity Park, Thane, Maharashtra, India. April 2018. Copyright ©Dinesh Valke/via wikipedia - CC BY-SA 2.0	Habit	Symphyotrichum novi-belgii (New York aster); flowering habit. Thane Biodiversity Park, Thane, Maharashtra, India. April 2018.	©Dinesh Valke/via wikipedia - CC BY-SA 2.0

Identity

Preferred Scientific Name

• Symphyotrichum novi-belgii (L.) G.L.Nesom

Preferred Common Name

• New York aster

Other Scientific Names

• Aster brumalis Nees
• Aster eminems Willd.
• Aster floribundus Willd.
• Aster johannensis Fernald
• Aster laevigatus Lam.
• Aster longifolius Lam.
• Aster novi-belgii L.
• Aster serotinus Willd.
• Aster tardiflorus L.
• Aster thyrsiflorus Hoffm.

International Common Names

• English: confused michaelmas daisy; michaelmas daisy
• Spanish: cielo estrellado; jarilla de jardin
• French: aster de jardins; Aster de la Nouvelle-Belgique; aster de Virginie

Local Common Names

• : Астра новобельгийская
• Czech Republic: hvězdnice novobelgická
• Denmark: almindelig sanct hansurt; almindelig sanct hansurt; bjerg-stenurt
• Estonia: oiekas aster
• Finland: isomaksaruoho; kalliomaksaruoho; kaukasianmaksaruho; särmämaksaruoho
• Germany: Gewöhnliche Glattblatt-Aster; Glattblatt- Aster; Neubelgische Aster
• Hungary: kopasz őszirózsa
• Italy: astro americano
• Japan: yuzen aster; yuzen-giku
• Lithuania: Virgininis astras
• Moldova: Стелуцэ Белжия-ноуэ
• Netherlands: Nieuw-Nederlandse Aster
• Norway: gewöhnliche glattblatt-aster; gravbergknapp; kantbergknapp
• Poland: aster nowobelgijski
• Slovakia: astra novobelgicka
• Slovenia: Virginijska nebina
• Sweden: kantig fetknopp; Kaukasiskt fetblad; röd kärleksört; stor fetknopp
• Ukraine: Айстра вiргiнська

EPPO code

• ASTNB (Aster novi-belgii)

Summary of Invasiveness

Symphyotrichum novi-belgii is a North American species which has become naturalized in parts of Europe, thriving in ruderal and waste areas, and mainly spreading vegetatively (BFIS, 2010). According to Hoffmann (1996), S. novi-belgii is considered as one of the most frequently occurring aster species in central Europe. Moreover, it belongs to these few exotic herbaceous perennials which are extensively naturalised in Britain and “demonstrate the breadth of morphological and reproductive strategies inherent in highly invasive species” as stated by Hitchmough and Woudstra (1999). According to their studies, a small number of prairie and woodland edge species have proved to be aggressive, among them S. novi-belgii which is widely naturalised and significantly increasing in the UK (Rich and Woodruff, 1996). According to several studies, S. novi-belgii is characterized as highly invasive (Michalkova, 2004; Novakova, 2008). Stace (1991) and Clement and Foster (1994) support that S. novi-belgii is now established in Great Britain and many other European countries.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Asterales
•                         Family: Asteraceae
•                             Genus: Symphyotrichum
•                                 Species: Symphyotrichum novi-belgii

Notes on Taxonomy and Nomenclature

Symphyotrichum is a genus of about 90 species of herbaceous plants in the family Asteraceae that were formerly treated within the genus Aster. The genus Aster historically included nearly 600 species in Eurasia and North America. A more recent treatment of the genus (Nesom, 1994) narrows its circumscription to about 180 species, almost all from Eurasia, with the North American species being moved to other related genera. The Eurasian species are characterized by larger sized and more symmetrically shaped chromosomes and the generally larger, 2-sided, glandular achenes. The North American species are made up of a number of distinct groups. By far the largest number of the North American species transferred from Aster to other genera by Nesom (1994) are now in Symphyotrichum, a genus originally established by the botanist Christian Gottfried Daniel Nees von Esenbeck and resurrected by Guy Nesom. The former Aster novi-belgii was transferred to Symphyotrichum novi-belgii, which is now the type species for the genus.

This species is a variable taxon, with several botanical varieties. Haines (2011) lists three varieties of Symphyotrichum novi-belgii found in New England: var. novi-belgii, var. elodes, and var. villicaule.

Several former and current Aster species and their hybrids, are commercially grown for cut flower production (Kadrnan-Zahavi and Yahel, 1985). Horticulturally they are all widely referred to as “asters” or “Michaelmas daisies”, reflecting their typical flowering period. The common name New York aster comes from its native status in this part of the USA. The species epithet novi-belgii means from New Belgium, a former name for the region between Virginia and New England in what became the USA.

Description

The following description is taken from the Flora of North America Editorial Committee (2016):

Perennials, 17–100(–140) cm, loosely to densely colonial or some­­times cespitose; long-rhi­zomatous. Stems 1–5+, erect (straight, stout to slender, often reddish), glabrous and hairy in lines distally or sometimes wholly strigoso-pilose (var. villicaule). Leaves thick, firm, ± fleshy, margins scabrous, apices mucronate, faces glabrous, abaxial midveins sometimes villosulous (var. villicaule); basal withering by flowering, petiolate (petioles winged, bases sheathing), blades ovate to ovate-lanceolate or lanceolate, 17–60+ × 6–11+ mm, bases attenuate to cuneate, apices obtuse; proximal cauline withering by flowering, sessile or widely winged-petiolate (petioles clasping), blades lance-ovate or -obovate to elliptic to linear-lanceolate, 40–200 × 4–40 mm, bases cuneate or sometimes slightly attenuate, sometimes rounded or slightly auriculate, slightly clasping, apices acute to acuminate; distal sessile, blades lance-ovate to linear-lanceolate, 13–62 × 3–15 mm, progressively reduced distally, bases cuneate or ± rounded, sometimes slightly auriculate, ± clasping, margins sparsely serrulate or entire. Heads in open to dense, paniculiform arrays, branches ± divaricate to ascending, leafy with remote, small, gradually reduced branch leaves. Peduncles 4–41 mm, glabrous or moderately pilose, bracts 1–3, lanceolate or ovate to linear-oblanceolate, subtending ones sometimes exceeding involucres, sometimes grading into phyllaries. Involucres campanulate, 6–9 mm. Phyllaries in 3–4 series, oblong-oblanceolate or -spatulate (outer) or oblong-lanceolate to linear-lanceolate or linear (inner), ± unequal to subequal, bases indurate  1 / 5 – 1 / 3 , margins hyaline, scarious, erose and sparsely ciliolate distally, green zones lanceolate, sometimes foliaceous, apices spreading to ± squarrose, usually acute to obtuse or ± long-acuminate, mucronulate, faces glabrous. Ray florets 15–35; corollas usually blue-violet or purple, rarely pink or white, laminae (6–)10–19 × 0.9–2.1 mm. Disc florets 28–68; corollas yellow becoming reddish brown to purple, 4–7.5 mm, tubes shorter than funnelform-campanulate throats, lobes lanceolate, 1–1.5 mm. Cypselae tan to brown, obovoid, compressed, 2–4 mm, 4–6-nerved, faces sparsely strigose to glabrate; pappi sordid to yellowish, 4–6 mm.

Distribution

S. novi-belgii is native to eastern Canada and the northeastern USA. Perennial North-American asters such as S. novi-belgii have become common in central Europe since the 17th century when they started to be cultivated as ornamental plants. Today, they are widely spreading especially in alluvial sites in the lowlands (Jedlicka and Prach, 2006). S. novi-belgii is considered as a naturalized alien in the Czech Republic (Pysek, 2003). In Belgium, it is among the species found recently in Brussels (1991-1994) that are absent from 1940-1971 plant lists (Godefroid, 2001). As well as being widely distributed in Europe, it has been found in countries including Japan, Australia and New Zealand: see Distribution Table for details.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

Like many other species later recognized as being invasive in central Europe, North-American perennial asters were also used first as ornamental plants. They have been cultivated since the 17th century (Hoffmann, 1996) and today many species of this large genus, including a high number of cultivars, are used in horticulture. Only Symphyotrichum lanceolatum [formerly Aster lanceolatus] and S. novi-belgii are considered to be widely naturalized in central Europe (Meusel and Jager, 1992). In considering the earliest possible date of the arrival of Aster at Wicken region (UK), it should be taken into account that Asters were introduced from eastern North America from 1633 onwards, with S. novi-belgii being brought into cultivation about 1710 (Wheldon, 1919; Green, 1974). It was first observed in the wild in Belgium in 1865 (BFIS, 2010).

Risk of Introduction

Globally, there can be a very few countries left where Asters have not already been introduced, but the risks of further introductions clearly remain very high, given the potential of this genus for a variety of uses and the lack of any wide-ranging prohibitions in its movement. Alluvial sites, abandoned fields and regions near flowing water should be taken into account as potential entries of these species. There is a high likelihood of deliberate introduction of S. novi-belgii because of its intended and wide use as an ornamental plant, and it can then be spread by fly-tipping of green waste (BFIS, 2010).

This species is not listed as a quarantined species, however it has a potential for further invasiveness and dispersal. Despite some limitations in growth, it is evident that S. novi-belgii tends to form large and dense colonies, which can persist over decades (Briggs et al., 1989), while it belongs to the most capable rhizomatous European aliens (Pysek, 2003). This combination of high seed production and intensive vegetative spread is generally highly effective in spread of species, and such plants were characterized as ‘superspecies’ by Huston and Smith (1987).

Habitat

In its’ native North America, S. novi-belgii is found growing in slightly brackish and tidal fresh marshes, occasionally borders of salt marshes; inland marshes, shrub marshes, shores and other moist areas (Tiner, 1987). Haines (2011) says that in New England, var. novi-belgii and var. elodes are found on coastal and near coastal habitats plus inland riverbanks, fens, marsh edges and boggy shores, while var. villicaule is usually found on rocky river shores. According to the Online Atlas of the British & Irish Flora (2016), in the UK it is naturalized on hedge banks, railway banks, roadsides, rubbish tips and waste ground, and sometimes occurs on lakesides and in fen vegetation. In Belgium it thrives mostly in ruderal and waste areas, especially on rich and moist soils, while it is less often observed in riparian habitats than other North American asters (BFIS, 2010).

S. novi-belgii spreads intensively in central Europe, becoming naturalized especially in alluvial sites along large rivers. Other invaded habitats include various disturbed and neglected sites, such as urban abandoned areas, road and railway banks (Jedlicka and Prach, 2006). It often invades abandoned sites and regions around flowing waters (Beniak et al., 2015). The species spreads rapidly along rivers, and it is not unusual to see large and dense growths on riverbanks and roadsides (Michalkova, 2004). In Poland and particularly Silesia-Cracow Upland, it is starting to colonize areas of former mining activity (Jędrzejczyk-Korycińska, 2004). 

Habitat List

Biology and Ecology

Genetics

S. novi-belgii has four botanical varieties: var. villicaule, var. crenifolium, var. novi-belgii and var. elodes (Flora of North American Editorial Committee, 2016). It sometimes hybridizes with Symphytrichum lanceolatum and S. lateriflorum (Flora of North American Editorial Committee, 2016). It has a sporophytic count of 2n=6x=48 (Labreque and Brouillet, 1996; Missouri Botanical Garden, 2015).

Reproductive Biology

Flowers are developed between June-August and October-November. Flowers are hermaphrodite and are pollinated by bees, butterflies, flies, beetles and moths (USDA, 2003). Its ability to flower depends on the following sequence of events: vernalization under winter cold, stem elongation and branching during the long days (LD, 16 h of light or more) of late spring and summer, flower initiation and flowering during the short days (SD, 10-16 h of light) of autumn (Wallerstein et al., 1992a; 1992b; Kristiansen et al., 1997). LD conditions inhibit flower initiation but induce shoot elongation and branching, while SD conditions induce flowering (Schwabe, 1985; Kadman-Zahavi and Yahel, 1985). Branched shoots, having been induced to flower under SD conditions, produce normal or abnormal terminal buds (inflorescence or involucre of bracts) when re-exposed to LD conditions. Since at least first-order branching is a prerequisite for flower initiation, rosette shoots will not flower under SD conditions or produce terminal buds following their transfer to LD conditions.

Simultaneously with flowering, a rosette type of growth develops from basal buds located below the soil surface, at the base of the flowering stem. In cold zones the rosette leaves freeze in winter, and growth resumes from the basal buds in spring. If the winter conditions are such that the rosette does not freeze (as in Israel), it will start to elongate in spring. Under Israeli conditions vernalization is not a prerequisite for elongation in S. novi-belgii (Kadrnan-Zahavi and Yahel, 1985).

S. novi-belgii produces large amounts of efficiently distributed seed, and is considered to be a self-incompatible species (East, 1940).

Physiology and Phenology

S. novi-belgii sexually (generatively) reproduces by seeds and non-sexually (vegetative reproduction) by underground stems called rhizomes (Michalkova, 2004). Therefore, S. novi-belgii is characterized as a rhizomatous plant which forms clonal patches (Cornelius, 1990; Chmielewski and Semple, 2001). According to Labrecque and Brouillet (1996) it is considered as a morphologically variable species and this variation appears to have both genetic and environmental bases.

Germination experiments show that most asters produce a relatively high number of viable and easily dispersed seeds, which often germinate immediately after ripening and usually do not require any special treatment. Low temperatures interrupt the germination of achenes in winter (Baskin and Baskin, 1979). S. novi-belgii, however, is generally considered to produce only a small amount of germinating seeds (Hoffmann, 1996). In Belgian climatic conditions, seeds do not seem to be able to mature (BFIS, 2010). When grown as an ornamental, seeds should be sown fresh in the autumn or spring (Heuser, 1997), with spring-sown seeds being chilled to improve germination (USDA, 2003).

Invasive asters possess a high capability of vegetative spread, while in already established polycorms, the rate of vegetative spread of clonal plants may be reduced (Harper, 1977). The vegetative spread of asters was very much reduced in compact soil (Schmid and Bazzaz, 1990). Chmielewski (1995) demonstrated very high phenotypic plasticity among clones, thus any findings cannot generalized. However, it is suggested that in suitable climatic conditions, S. novi-belgii can spread easily by seed over a long distance and, after its establishment, can spread fast vegetatively, monopolizing the space. From eight clones of S. novi-belgii the percentage of immediately germinated achenes was between 83.3 and 96.6 %, while after storage at 20°C germination percentages of most clones were further increased (Jedlicka and Prach, 2006).

Rhizome fragments of S. novi-belgii clones of a length of 10 cm with developing basal leaves of terminal rosettes can be put 5 cm deep in order to give new plants. Some aster clones produced more than 100 new rosettes from one initial rosette within a year. Apparently, S. novi-belgii forms large polycorms in a relatively short time, however the role of vegetative growth has not been extensively studied. It should be noticed that their rapid vegetative spread and biomass production of S. novi-belgii can be significantly reduced by competition from established vegetation (weeds) as shown by Jedlicka and Prach (2006).

Environmental Requirements

This plant requires well-drained soil and prefers sandy, loamy and clay soils. It can grow on nutritionally poor soil, in semishade or no shade but prefers a sunny location (USDA, 2003). S. novi-belgii grows usually at lower altitudes in lowlands and hilly areas. It tolerates a wide range of environmental conditions and quickly colonizes recently disturbed sites.

Climate

Notes on Natural Enemies

Dowson (1923) found that different species of Aster (the then wider genus) varied in their degree of susceptibility to diseases, the most susceptible being varieties of S. novi-belgii. S. novi-belgii vars 'Rufus', 'Snowsprite' and 'Climax' were found to be extremely susceptible to Phialophora asteris (Burge and Isaac, 1974).

Means of Movement and Dispersal

S. novi-belgii has been widely distributed through intentional introduction as an ornamental plant. For neighbouring regions, local movements were often by means of accidental introduction (trade and transport, garden escape etc) or natural dispersal (DAISIE, 2016). It can be dispersed by fly-tipping of green waste followed by vegetative spread (BFIS, 2010). In parts of its alien range it does not produce viable seeds and so relies on vegetative spread (BFIS, 2010), but where seeds developed these can be spread by wind, aided by tufts of hair on the seed.

Environmental Impact

Asters easily form dense and wide monospecific colonies displacing native wetland plants, favouring sedimentation and stabilisation of riverbanks which reduces the ability of rivers to meander and flood (BFIS, 2010). Hejda et al. (2017) report that the richness of native species decreases as S. novi-belgii cover increases in the invaded range in central Europe. BFIS (2010) lists the primary impact on species as being through competition, and suggests that it is likely to affect natural succession of ecosystems.

S. novi-belgii has been described as an invasive species of limited distribution in Central Russia but which may cause environmental problems (Vinogradova et al., 2010). Regarding its negative impacts, it exhausts the soil on which it grows (Green, 1974). On the positive side, the species is known for attracting butterflies and moths to areas where it is found growing, and is a good bee plant providing nectar in the autumn (USDA, 2003).

Risk and Impact Factors

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerant of shade
• Long lived
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Reproduces asexually
• Has high genetic variability

• Modification of nutrient regime

• Rapid growth

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Highly likely to be transported internationally illegally
• Difficult to identify/detect as a commodity contaminant

Uses

S. novi-belgii is an important ornamental plant, and also has many medicinal properties. In a study conducted by Hooper and Chandler (1984), S. novi-belgii was found to contain campesterol and β-sitosterol as well as the amyrins and lupeol. 

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

For the chemical control of S. novi-belgii as an invasive plant, several non-selective herbicides could be used (eg glyphosate, glufosinate, diquat), since it has not yet entered any crops. Some other herbicides such as picloram and 2,4-D have been used for the control of similar species like Chloracantha spinosa [formerly Aster spinosus Benth.] (Gonzalez et al., 2010). However, risks of herbicide resistance development should be also taken into account since biotypes of Aster squamatus were found to be resistant to the ALS-inhibiting herbicide imazapyr after 10 years of use in Seville, Spain (Osuna et al., 2003).

S. novi-belgii can be controlled by means of tillage, however ploughing should be done in depths more than 15-20 cm, because of the rhizomes of the plant which should either come in the soil surface (in order to be burnt by sun) or move to greater depths. It is recommended to avoid planting this species near rivers and wet habitats, especially near protected areas (natural reserves, Natura 2000 sites, etc.) and to put a rhizome barrier in order to limit lateral expansion. In Belgium, introduction is prohibited within and nearby protected sites and areas of high biological value and in the vicinity of watercourses (Moniteur Belge, 2013).

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Contributors

29/02/2016, Original text by:

Dr Ilias Travlos, Agricultural University of Athens, Athens, Greece

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