Cotoneaster dielsianus E. Pritzel, Bot. Jahrb. Syst. 29: 385, 1900.
Synonym: C. applanatus Duthie ex Veitch
Section Franchetioides, series Dielsiani
Origin: China (Sichuan, Hubei).
Presence in western Europe: Naturalized in Austria and Germany (John & Frank 2008; Dickoré & Kasperek 2010), Great Britain (Stace 2010) and Sweden (Hylmö 1993). Furthermore known from France (see for instance Verloove 2007). Doubtlessly present in large parts of Europe.
Cultivation in Belgium and the Netherlands: “common” (De Koning & van den Broek 2009).
Comparative taxonomy: Cotoneaster dielsianus is here accepted in a narrow sense, following Fryer & Hylmö (2009). Dickoré & Kasperek (2010) and Flora of China (Lingdi & Brach 2003) accept this species in a wider sense. Both subsume most species of Fryer & Hylmö’s (l.c.) series Dielsiani (and even some species of other series viz Franchetioides and Sterniani) under Cotoneaster dielsianus. Indeed, Cotoneaster dielsianus is fairly variable in Belgium and some of the (micro-) species might have been overlooked (see below). Dickoré & Kasperek (2010) surprisingly include Cotoneaster fangianus under this species. The latter is rather different and is much more reminiscent of Cotoneaster zabelii (both belong with Section Cotoneaster, series Zabelioides). Cotoneaster vilmorinianus G. Klotz is accepted as a synonym of C. franchetii by Dickoré & Kasperek (2010) while it is included in C. dielsianus (var. dielsianus) by Lingdi & Brach (2003).
Illustrations: Hylmö (1993), Grevtsova (1999), Henker & Kiesewetter (2006), Roloff & Bärtels (2006), John & Frank (2008), De Koning & van den Broek (2009), Fryer & Hylmö (2009), Stace (2010). See also: http://www.british-wild-flowers.co.uk/C-Flowers/Cotoneaster,%20Diel%27s.htm.
Cotoneaster dielsianus is one of the commoner species in Belgium, in cultivation as well as in the wild. It was perhaps first reliably documented in 1962 when it was collected on a calcareous slope in Buzenol (Montauban). In the past decades it has been increasingly recorded in numerous, very widely scattered localities in Belgium, in Flanders as well as in Wallonia. Although Cotoneaster dielsianus is one of the most frequently found species of the genus in Belgium, it mostly occurs with single shrubs. Small but more or less stable populations are rare and seem to be restricted to warmer and drier areas, especially near the coast (compare with Dickoré & Kasperek 2010).
Cotoneaster dielsianus grows in a very wide range of natural and artificial habitats. It has been recorded in full shade as well as in sun-exposed localities and on both calcareous and acidic substrate. At present it is probably only genuinely naturalized in coastal scrub (especially near De Haan and Oostduinkerke) and in dry woodland (usually by tracks, most often in deciduous woodland but also under Pinus), perhaps locally also on coal mining heaps. Cotoneaster dielsianus has furthermore been observed in the following artificial habitats: abandoned railway yards and in railway sidings, on top of old walls (including quay walls), in disused gravel pits, on canal banks and in derelict industrial areas. In 2011 it was also discovered on a sun-exposed calcareous slope adjoining the canal Kortrijk-Bossuit in Moen (a single shrub).
Cotoneaster dielsianus is a fairly variable species, especially with regard to leaf dimensions and pubescence. From most species currently found in the wild in Belgium Cotoneaster dielsianus is best distinguished by its (mostly) deciduous, relatively small leaves with densely grayish tomentose lower sides and acute to shortly acuminate apices, its distinctly arching branches, its red berries with usually 4 nutlets (rarely 3 or 5), its inflorescence with ca. 3-7 flowers with closed, pinkish-red corollas, etc. Cotoneaster dielsianus can be mistaken with the superficially similar C. franchetii. Indeed, while the indumentum of the lower leaf surface typically is greyish in Cotoneaster dielsianus, it sometimes tends towards the more whitish tomentum of the latter (see under the latter for differences and also Dickoré & Kasperek 2010). Confusion is furthermore possible with Cotoneaster fangianus and C. zabelii. However, these two species have fruits that are pendent on long pedicels, only 2 nutlets per berry (or more rarely 1 or 3), leaves that are more or less rounded at apex, etc. Finally, Cotoneaster dielsianus may be confused with native C. integerrimus, especially in natural habitats (calcareous outcrops) where the latter occurs. Both are opposed in the table beneath:
|
C. dielsianus |
C. integerrimus |
|
Hypanthium and fruit persistently tomentose-strigose |
Hypanthium and fruit glabrous |
|
Usually 4 nutlets per berry (rarely 3 or 5) |
Usually 3 nutlets per berry (rarely 2 or 4) |
|
Inflorescence with 3-7(-10) flowers |
Inflorescence with (1-)3-4(-6) flowers |
|
Leaves 21-26 x 11-26 mm |
Leaves 32-55 x 21-38 mm |
Cotoneaster dielsianus itself is a very variable species and insufficiently understood. Some related (micro-) species might have been overlooked, especially Cotoneaster bradyi E.C. Nelson & J. Fryer, C. elegans (Rehder & E.H. Wilson) Flinck & B. Hylmö, C. floridus J. Fryer & B. Hylmö and C. splendens Flinck & B. Hylmö. The latter is commonly cultivated in Belgium and the Netherlands (De Koning & van den Broek 2009) and likely to be encountered in the wild. Its fruits are orange-red (instead of red) and its leaves are paler green with a densely pilose lower leaf surface (not tomentose). The same applies to Cotoneaster elegans (“in Kultur sehr häufig”, according to Klotz 1957). Plants with small leaves (ca. 15 mm long), often with a rather dullish upper surface possibly pertain to one of these species. The type of Cotoneaster dielsianus has similar leaf dimensions (15 x 10 mm) while plants in cultivation usually have larger (and narrower) leaves and more richly-flowered inflorescences (Klotz 1957).
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Literature
De Koning J. & van den Broek (2009) Nederlandse Dendrologie (14th ed.). K.N.N.V.: 547 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].
Fryer J. & Hylmö B. (2009) Cotoneasters. A comprehensive guide to shrubs for flowers, fruit, and foliage. Timber Press, Portland-London: 344 p.
Grevtsova A.T. (1999) Atlas Cotoneasters. Cotoneaster (Medic.) Bauhin. Kiev, House Orchard, Truck-Garden: 372 p.
Henker H. & Kiesewetter H. (2006) Erstnachweise kritischer Pflanzensippen für Mecklenburg-Vorpommern (Blütenpflanzen). Bot. Rundbr. Mecklenburg-Vorpommern 41: 5-20.
Hylmö B. (1993) Oxbär, Cotoneaster i Sverige. Svensk Bot. Tidskr. 87: 305-330.
John H. & Frank D. (2008) Verwilderte Cotoneaster-Arten in Halle (Saale) und Umgebung. Mitt. Florist. Kart. Sachsen-Anhalt 13: 3-28 [available online at: http://bv-st.de/images/Flo-Kart_2008_003-028_John_Frank.pdf
Klotz G. (1957) Übersicht über die in Kultur befindlichen Cotoneaster-Arten. Wiss. Z. Univ. Halle, Math.-Nat. 6(6): 945-982.
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].
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Stace C. (2010) New Flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Verloove F. (2007) La flore urbaine de Dunkerque (Nord): quelques xénophytes remarquables. Monde Pl. 494: 11-14 [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/flore%20urbaine.pdf].