Cotoneaster hjelmqvistii Flinck & B. Hylmö, Watsonia 18: 312, 1991.
Section Adpressi, Series Horizontales
Origin: China (Gansu).
Presence in western Europe: Naturalized in Great Britain (Stace 2010) and Germany (Dickoré & Kasperek 2010; sub C. apiculatus). Also known as an escape from France (dep. Nord, LG!; see also Farille & al. 2010) and from Scandinavia (Karlsson 2002). Doubtlessly widely overlooked for C. horizontalis.
Cultivation in Belgium and the Netherlands: “very common” (De Koning & al. 2000). Cotoneaster hjelmqvistii was initially introduced in the nursery trade by the Belgian nursery Vuyk Van Nes in 1954 (Fryer & Hylmö 2009).
Comparative taxonomy: Dickoré & Kasperek (2010) include Cotoneaster hjelmqvistii in a broadly circumscribed C. apiculatus Rehder & E.H. Wilson in Sargent. Although it is an endemic of China, it is not mentioned by Lingdi & Brach (2003), not even as a synonym.
Illustrations: Macpherson & Lindsay (1993), De Koning & al. (2000), Fryer & Hylmö (2009), Stace (2010). See also: http://www.british-wild-flowers.co.uk/C-Flowers/Cotoneaster,%20Hjelmqvist's.htm.
Cotoneaster hjelmqvistii has long been confused with C. horizontalis in Belgium (and elsewhere in western Europe). It was probably first collected in spontaneous woodland on calcareous slopes by the Albertkanaal near Lanaye (Thier de Nivelle) in 1984. By now it has become a rather widespread species that is known from numerous localities in Belgium. Moreover, it is still much confused with Cotoneaster horizontalis and likely to be commoner than generally admitted. It has been observed in a very wide range of habitats in Belgium, ranging from natural ones (calcareous slopes, coastal dunes, deciduous woodland) to highly artificial ones (coal mining heaps, quarries, former ash, gypsum or chalk deposits, abandoned railway yards, old walls, foot of fences, hedges or pergolas in gardens, cemeteries, etc.). Cotoneaster hjelmqvistii was also seen as an epiphyte in pollard willows (Salix) in Tielt. It often occurs as single or scattered bushes but obviously naturalized populations have been observed as well, for instance on the verge of an abandoned quarry in Ecaussinnes (with Cotoneaster rehderi) or in spontaneous woodland on a former ash deposit in Hemiksem (Kallebeekbos). Cotoneaster hjelmqvistii also occurs on dry, sun-exposed calcareous slopes, a habitat that is increasingly invaded by C. horizontalis in Belgium (Picqueray & al. 2008; see also http://ias.biodiversity.be/species/show/49). In the nature reserve Vaarttaluds in Moen – a hotspot for Orchidaceae – both species co-occur and exhibit the same invasive behaviour. Although genuine Cotoneaster horizontalis doubtlessly is the prevalent invasive species in grasslands on calcareous soils, at least in part of them C. hjelmqvistii also occurs, often without being noticed so far. It furthermore grows in several localities in coastal dunes, often in nature reserves (for instance Houtsaegherduinen, Plaatsduinen, also in Willemspark, Witte Burg, etc.) but usually in small number.
Cotoneaster hjelmqvistii looks like a robust form of C. horizontalis and it is frequently sold as cv ‘Robusta’ of the latter (De Koning & al. 2000, Fryer & Hylmö 2009; see also Flinck & Hylmö 1991). However, they are easily told apart: the former is usually taller, often with more erect, arching and flexuous branches with branchlets much less densely set (hence a less distinct herringbone pattern) and its leaves are always larger, almost orbicular, more papery, early turning reddish and dropping in autumn (by mid-October). These and some additional useful features are summarized in the table beneath. A recently described related species, Cotoneaster spongbergii Fryer & Hylmö, might have been overlooked. It is frequently grown in Europe and distributed by the Dutch nursery trade (see Fryer & Hylmö 2009). It has slightly smaller leaves (10-16 x 6-11 mm) and verruculose branches.
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Cotoneaster hjelmqvistii |
C. horizontalis |
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Leaves almost orbicular, 13-25 x 10-25 mm, obtuse with mucronate apex, chartaceous (papery) and early turning reddish and dropping (by mid-October) |
Leaves smaller, 5-12 x 5-9 mm, shortly acuminate to acute at apex, rather coriaceous (leathery) and not dropped before winter |
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Taller plant, often with more erect, arching and flexuous branches with branchlets not densely set (herringbone pattern not very distinct) |
Smaller, decumbent-ascending plant with branchlets very closely set (very distinct herringbone pattern) |
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Nutlets 2(-3) per berry |
Nutlets (2-)3 per berry |
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Hypanthium soon becoming glabrous (glabrescent) |
Hypanthium sparsely pilose-strigose |
Literature
De Koning J., van den Broek J.W., Van De Laar H.J. & Fortgens G. (2000) Nederlandse Dendrologie (13e druk, geheel herzien). Veenman & Zonen, Ede: 585 p.
Dickoré W.B. & Kasperek G. (2010) Species of Cotoneaster (Rosaceae, Maloideae) indigenous to, naturalising or commonly cultivated in Central Europe. Willdenowia 40: 13-45 [available online at: http://user.uni-frankfurt.de/~kasperek/papers/dickore_kasperek_2010.pdf).
Farille M.A., Zeller J., Jordan D., Charpin A. & Garraud L. (2010) Cotonéasters échappés de jardins en Haute-Savoie. Monde Pl. 501: 1-5.
Flinck K.E. & Hylmö B. (1991) Two new species of Cotoneaster. Watsonia 18: 311-313 [available online at: http://www.watsonia.org.uk/Wats18p311.pdf] .
Fryer J. & Hylmö B. (2009) Cotoneasters. A comprehensive guide to shrubs for flowers, fruit, and foliage. Timber Press, Portland-London: 344 p.
Karlsson T. (2002) Nyheter i den svenska kärlväxtfloran II. Korsblommiga–flockblommiga. Svensk Botanisk Tidskrift 96: 186-206. [available online at: http://sbf.c.se/www/pdf/96(3-4)/Karlsson.pdf]
Lingdi L. & Brach A.R. (2003) Cotoneaster. In: Wu Z.Y. & Raven P.H. (eds.), Flora of China, vol. 9. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 85-108 [available online at: http://flora.huh.harvard.edu/china/PDF/PDF09/Cotoneaster.PDF].
Macpherson P. & Lindsay E.L.S. (1993) Cotoneasters in the Glasgow Section of V.C. 77. Glasg. Nat. 22(2): 111-114.
Picqueray J., Vanderhoeven S. & Mahy G. (2008) Naturalization and impact of a horticultural species, Cotoneaster horizontalis (Rosaceae) in biodiversity hotspots in Belgium. Belg. Journ. Bot. 141(2): 113-124.
Stace C. (2010) New Flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.