Classification
 Nomenclature
Scientific Name:
Cotoneaster Medik., Philos. Bot. (Medikus) 154 (1789)
Type Taxon:
Cotoneaster integerrimus Medik.
 Description

Shrubs to small trees; erect, procumbent or prostrate; deciduous, semi-deciduous or evergreen. Branches unarmed, red-brown or grey-brown. Leaves alternate or alternate on short fascicles, simple, shortly petiolate; stipules subulate, red or green; margin of leaf blade entire. Inflorescences terminal and axillary, on short fascicles of 2–6 leaves; solitary, in simple corymbs, or forming compound corymbs. Hypanthium adnate to ovary. Sepals 5, persistent, usually invested in hairs. Petals 5, erect or spreading, imbricate in bud, white, pink or red, with or without a tuft of hairs near the inner base. Stamens 10–20(22), inserted in mouth of the hypanthium. Ovary inferior or semi-inferior, 2–5-loculed; carpels 2–5, free, rarely 2 fused into 1; styles 1 per carpel, free; stigmas dilated. Fruit a pome, red, orange or purple-black, with persistent, incurved, fleshy sepals, containing pyrenes; pyrenes 1–5, stony, 1-seeded; seeds hemispherical or triangular in cross-section, style at apex or with an umbo above the style attachment point.

 Key

Names in brackets are species not currently known to be present in New Zealand but were formerly present and may still be in cultivation.

1leaf undersurface dense with fine, woolly hairs which completely hide the underleaf surface, the hairs persisting throughout the life of the leaf, the woolly layer of old leaves often dirty grey or brown 2
leaf undersurface with sparse to moderately dense hairs, underleaf surface easily visible, particularly in old leaves5
2petals spreading, white; pyrenes (1)2 per fruit, style attached at pyrene apex C. pannosus
petals erect, white, pink, or red centrally and pink on margins; styles/pyrenes 2–4(5) per fruit, style attached below pyrene apex3
3styles/pyrenes (3)4(5); plants deciduous [C. dielsianus]
styles/pyrenes 2–3; plants evergreen or semi-deciduous4
4leaf lamina 17–20 × 9–10 mm; fruit 5.9–6.0 mm diameter; petals 2.8 mm wide, white with slight pink tinting on some petals; styles/pyrenes 3C. amoenus
leaf lamina 30–38 × 13–22 mm; fruit 7.0–9.6 mm diameter; petals 3.4–3.7 mm wide; styles/pyrenes equally 2 or 3C. franchetii
5leaves rugose to some degree (lamina weakly to strongly convex between veins, seen from above)6
leaves not rugose (veins may be impressed but lamina is not convex between the veins seen from above)12
6leaves strongly rugose, slightly glaucous or not glaucous on underside of leaf, deciduous7
leaves moderately to weakly rugose, distinctly glaucous on underside of leaf, evergreen8
7fruit red; inflorescence of 5–37 flowers; styles/pyrenes 4–5C. bullatus
fruit black; inflorescence of 5–9 flowers; styles/pyrenes 2–3(4) [C. moupinensis]
8leaves elliptical to obovate, apex obtuse; style usually attached 0.4–0.8 mm below pyrene apex, pyrene umbonate9
leaves elliptical to narrowly elliptical, apex acute; pyrene with acute apex terminating in the style10
9lamina 64–92 mm × 31–50 mm, tending obovate, not V-shaped in cross-section, surface weakly but distinctly rugose, olive green to dark green, never with a red-brown margin, midvein on leaf underside never red-tinted in autumn and winter; fruit 6.2–8.4 mm in diameterC. coriaceus
leaves 58–69 mm × 24–33 mm, tending elliptical, often distinctly V-shaped in cross-section, surface very weakly rugose or plane, olive green, commonly with a red-brown margin, midvein on leaf underside usually red-tinted in autumn and winter; fruit 4.5–6.4 mm in diameterC. glaucophyllus
10leaves elliptical, 19–39(44) mm wide, moderately rugose, leaf margins not or indistinctly recurved; fruit 10–11 mm in diameterC. ×watereri
leaves narrowly elliptical, 13–26 mm wide, strongly rugose, leaf margins recurved; fruit 5–7 mm in diameter 11
11petals white and spreading C. salicifolius
petals pink and semi-erect C. hylmoei
12leaf undersurface not glaucous, with sparse, coarse, straight hairs that persist; petals pink to red and erect; anthers white; style inserted below the ovary apex; styles/pyrenes 2–413
leaf undersurface distinctly glaucous, hairs on underside either coarse, straight, and persistent or fine, woolly, and not persistent on old leaves; petals pink or white and erect or spreading; style inserted at pyrene apex or below apex; styles/pyrenes 1–517
13branches in flattened planes; stipules not persistent or obvious; stamens 11–15; filaments dark pink to red; fruit vivid red to vivid reddish-orange, navel closed; styles/pyrenes 2–3(4)14
branches not in flattened planes; stipules persistent and obvious; stamens 18–20; filaments white, turning pink; fruit vivid reddish-orange, navel open due to calyx lobes projecting; styles/pyrenes 3–416
14plant an upright shrub; leaves densely but not distichously arranged on ultimate branchlets; leaves plane or only slightly V-shaped in cross-section, 12–31 mm long, 8–17 mm wide, moderately glossy, stamens 11–15; styles/pyrenes 2–4C. divaricatus
plant more or less prostrate and spreading or cascading; leaves glossy, plane or V-shaped in cross-section; stamens 8–17; styles/pyrenes 2–3(4)15
15leaves distinctly V-shaped in cross-section, elliptic, lamina 10–14 mm long, 6–8 mm wide, upper surface very glossy; stamens 8–11; fruit 5.8–6.4 mm diameter, styles/pyrenes invariably 3C. perpusillus
leaves plane, orbicular, largest leaves with lamina 12–29 mm long, 9–16 mm wide, upper surface glossy; stamens 12–17; fruit 6.0–10.0 mm diameter, styles/pyrenes equally 2 or 3, rarely 4C. horizontalis
16leaves semi-deciduous, lamina 24–35 mm long, 15–19 mm wide, thick (250–400 µm); branches stiffly erect to spreading; styles/pyrenes 3–4C. simonsii
leaves deciduous, 18–23 mm long, 8.5–11.0 mm wide, thin (210–240 µm); branches spreading horizontally and drooping toward their tips; styles/pyrenes 3–4C. marquandii
17plant a low or prostrate shrub, commonly with divaricating (springy, interlacing branches); leaves mostly small (leaf lamina 5–27 mm long), with straight, persistent hairs18
plant an erect shrub to small tree, branches spreading and often arching; leaves commonly medium to large (leaf lamina most commonly over 50 mm long, but as small as 14 mm long), with woolly hairs that become sparse on old leaves22
18leaves small, lamina 5–10 mm long, upper leaf surface very glossy, apex emarginate19
leaves medium, lamina 10–51 mm long, upper leaf surface glossy to dull, apex acute to obtuse, sometimes appearing emarginate due to V-shape in cross-section20
19leaf lamina 5.3–10.0 mm long, 3.3–6.0 mm wideC. microphyllus
leaf lamina 5.4–5.6 mm long, 2.3–2.9 mm wideC. thymifolius
20styles/pyrenes invariably 2; leaf lamina 10–18(21) mm long, 4.5–10 mm wide, apex acute to emarginateC. integrifolius
styles/pyrenes 2–4(5); leaf lamina 15–27 mm long, 7.2–27 mm wide; apex obtuse21
21styles/pyrenes (4)5; leaf lamina 23–51 mm long; flower pedicel 3–23 mm long C. dammeri
styles/pyrenes 2–4 and variable on the same plant; leaf lamina 15–27 mm long; flower pedicel 1.5–10 mm long C. ×suecicus
22erect, deciduous tree; leaves large (lamina 56–114 mm long, 30–75 mm wide), leaf underside slightly glaucous; styles/pyrenes 2, pyrene hairs dense23
erect deciduous or evergreen shrub; leaves medium-sized (lamina 14–40 mm long, 11–26 mm wide), dull above, leaf underside glaucous; styles/pyrenes 1–5; pyrene hairs sparse24
23leaves dull on upper surface; petals with hair tuft present or absent; anthers purple; fruit red, navel closedC. frigidus
leaves semi-glossy on upper surface; petals with hair tuft present; anthers white; fruit purple-black, navel wide openC. bacillaris
24leaf lamina 14–20 × 10–11 mmC. sherriffii
leaf lamina 22–46 × 18–26 mm25
25leaf glossy above, evergreen; petals erect, pink, glabrous; filaments pink; anthers white, pyrenes (1)2[C. roseus]
leaf dull or semi-glossy above, deciduous; petals spreading, white, with tuft of hairs; filaments white; anthers white, pink, or purple; pyrenes 1 or 226
26lamina 31–46 mm long, elliptical; hypanthium hairs sparse; stamens 19–20; anthers pink to pinkish-purple, styles/pyrenes 1(2)C. hebephyllus
lamina 22–30 mm long, orbicular; hypanthium hairs dense; stamens 13–15; anthers white; styles/pyrenes 2C. soongoricus
 Distribution

About 90–500 species that are widespread in temperate North Africa, Asia, Central America (Mexico), and Europe, most abundant in the Chinese Himalaya (Szechuan and Yunnan provinces).

 Biostatus
Exotic
Number of species and named hybrids in New Zealand within Cotoneaster Medik.
CategoryNumber
Exotic: Fully Naturalised10
Exotic: Casual8
Exotic: Cultivated6
Total24
 Cytology

n = 17 is regarded as basic (Fryer & Hylmö 2009), 2n = 34 diploid, 2n = 51 triploid, 2n = 68 tetraploid, 2n = 85 pentaploid, 2n = 102 hexaploid. Fryer & Hylmö (2009) state that 10% of species are diploid, 70% tetraploid, 15% pentaploid, and a few have higher ploidy than pentaploid. They also conclude that diploid species are outbreeding and variable while tetraploid species are apomictic and uniform in morphology. Dickoré & Kasperek (2010) believe apomixis has usually been inferred from the uniformity of seed progeny rather than investigation of how the embryo is created. Triploidy is extremely difficult to achieve in plants, and most cases of triploidy are in fact hexaploids. The presence of so-called triploids in Cotoneaster suggests that the base number in Cotoneaster is lower than 17 and that the triploids are actually hexaploids (P. Heenan, pers. comm.).

 Notes

Webb et al. (1988) provided descriptions of 5 fully naturalised and 2 casual Cotoneaster species. This treatment provides descriptions of 12 fully naturalised and 5 casual Cotoneaster species or hybrids.  This increase over 29 years reflects the tendency of species in the genus to escape from cultivation and to naturalise.  For this reason, a further 6 species in cultivation have been included.

Flowers and fruit can be used equally well to determine the number of embryos per flower or fruit. Therefore this feature is cited in the key as "styles/pyrenes".  The number of embryos per flower or fruit varies on a plant.  It is therefore best to count the styles or pyrenes of c. 6–8 flowers or fruit to establish the average embryo number.

Fresh leaf thickness is given in microns, because perception of leaf thickness is influenced by leaf size; larger leaves give the impression of being thinner than they actually are.

The following qualifiers are used for hair density. Dense = surface not visible; moderately dense = surface partly obscured but still visible; sparse = hairs scattered across the surface.

Flowers per corymb refers to the number of flowers per lateral fascicle; the number on the terminal fascicle is always much greater.

RHS colour numbers follow the RHS colour charts (Royal Horticultural Society 1966). Colour names are Universal Colour Language names (Kelly & Judd 1976; http://www.december.com/html/spec/colorucl.html). RHS colour charts are available online at the Royal Horticultural Society website (http://rhscf.orgfree.com) and the Azalea Society of America website (http://azaleas.org/index.pl/rhsmacfan1.html). Both vary in terms of how well they match RHS printed colour charts: they are reasonably accurate in the reds but a poor match in the greens.

 Bibliography
Connor, H.E.; Fountain, J. 2009: Plants that Poison: A New Zealand Guide. Manaaki Whenua Press, Lincoln.
Dickoré, W.B.; Kasperek, G. 2010: Species of Cotoneaster (Rosaceae, Maloideae) indigenous to, naturalising or commonly cultivated in central Europe. Willdenowia 40(2): 13–45.
Fryer, J.; Hylmö, B. 2009: Cotoneasters: a comprehensive guide to shrubs for flowers, fruit, and foliage. Timber Press, Portland.
Kelly, K.L.; Judd, D.B. 1976: Color universal language and dictionary of names. National Bureau of Standards special publication 440. US Department of Commerce, Washington, DC.
Lo, E.Y.; Donoghue, M.J. 2012: Expanded phylogenetic and dating analyses of the apples and their relatives (Pyreae, Rosaceae). Molecular Phylogenetics and Evolution 63: 230–243.
Mabberley, D.J. 2008: Mabberley's plant book, a portable dictionary of plants, their classification and uses. Edition 3. Cambridge University Press.
Medikus, F.K. 1789: Philosophische Botanik. Vol. 1. der neuen Hofund Akademischen Buchhandlung, Mannheim.
Royal Horticultural Society 1966: R.H.S. colour chart. Royal Horticultural Society of Great Britain, London.