Sorbus
Rosaceae tribe Maleae
alisier, mountain-ash, rowan, service tree, sorbier, whitebeam
1–8, erect or ascending;
bark gray to brown or bronze, usually smooth, becoming scaly with age, with conspicuous horizontal lenticels; long and short shoots present; unarmed;
twigs with smell and taste of bitter almond (cyanogenic glycosides); glabrous or hairy.
deciduous, cauline, simple or odd (rarely even) pinnately lobed or divided;
stipules usually early deciduous, sometimes persistent, free or short-adnate to petiole, linear, ovate to lanceolate, or flabellate, margins entire or dentate to laciniate;
petiole present;
blade ovate to oblong, 5–33 cm, membranous to slightly leathery, leaflets 0 or 7–17(–19), usually opposite, rarely alternate, elliptic, ovate, oblong to lanceolate or oblanceolate, margins flat, sharply serrate to nearly entire, venation pinnate, surfaces glabrous or hairy, sometimes glaucous.
alternate, simple or pinnately compound;
stipules persistent, deciduous, or absent, free, sometimes adnate or short-adnate to petiole (and base of blade in Peraphyllum );
venation pinnate.
terminal, 6–400+-flowered, panicles, flat-topped or rounded, glabrous, glaucous, or hairy;
bracts present;
bracteoles absent.
present.
opening after leaf expansion, perianth and androecium epigynous or 1/2 epigynous, odor strong, often considered unpleasant or rancid, 5–17 mm diam.;
hypanthium green to red, obconic, 2–6 mm, glabrous or hairy;
sepals 5, erect or ascending, ovate or triangular;
petals 5, white or pink [red], suborbiculate or broadly obovate to broadly ovate, base clawed or not, claw often ± villous;
stamens [10–]14–20[–44] in 2 or 3 series, usually slightly longer than petals;
carpels 2–5, distinct, partially or wholly connate and adnate to all or proximal 1/2 of hypanthium, usually apically woolly, styles 2–5, terminal, distinct or connate 1/2 of length;
ovules 2 or 3[or 4] (all but 1 usually aborting).
perianth and androecium epigynous (perigynous in Vauquelinia );
epicalyx bractlets absent;
hypanthium hemispheric, campanulate, cupulate, funnelform, or obconic, sometimes urceolate, cylindric, or saucer-shaped;
torus absent (present in Vauquelinia );
carpels 1–5, ± connate or distinct, adnate more than 1/2 to hypanthium (free in Vauquelinia , [Dichotomanthes ]), styles terminal, sometimes subterminal or lateral, distinct or ± connate basally;
ovules (1 or)2(or 3), basal and collateral, or 2–20+, marginal and biseriate (with funicular obturators).
pomes, usually orange or red, rarely brown or yellow [green, white, or pink], globose to ovoid, obovoid, ellipsoid, or oblong, [pyriform], 4–19 mm, smooth or with lenticels, shiny, sometimes glaucous, hairy or glabrous;
flesh usually with sclereids;
hypanthium persistent;
sepals usually persistent, rarely deciduous, usually incurved, fleshy;
carpels cartilaginous;
styles often persistent.
pomes or woody capsules surrounded by hypanthium and splitting into 5 follicles (coccetum) (Vauquelinia);
styles persistent or deciduous, not elongate.
3–5, brown to reddish brown or yellowish, darkening with maturity, ovoid to lanceoloid, slightly asymmetric and flattened.
= 17.
Sorbus
Rosaceae tribe Maleae
Species ca. 130 (10 in the flora).
The taxonomy of Sorbus is complicated by apomixis, polyploidy, and hybridization among sections and genera, especially in Eurasia. Hybrids with other genera in Maleae are generally distinguished by their incompletely divided, deeply lobed leaves, and include ×Amelasorbus Rehder (Sorbus × Amelanchier), ×Crataegosorbus Makino (Sorbus × Crataegus), ×Sorbaronia C. K. Schneider (Sorbus × Aronia), ×Sorbocotoneaster Pojarkova (Sorbus × Cotoneaster), ×Sorbopyrus C. K. Schneider (Sorbus × Pyrus), and ×Tormimalus Holub (as Torminalis Medikus [= Sorbus subg. Torminaria] × Malus). Only ×Amelasorbus and ×Sorbaronia are known to occur naturally in North America. Parentages of some reported ×Sorbaronia nothospecies are difficult to verify, especially for densely hairy hybrids involving either Aronia arbutifolia, A. ×prunifolia (Marshall) Rehder, or Sorbus aucuparia; all these possibilities are claimed. In addition to their partially pinnate leaves, some ×Sorbaronia hybrids may be recognized by the presence of pink to red anthers and black or purple fruits; these are reported also to be somewhat sterile.
Diploid Sorbus are often obligate outcrossers; some apomictic triploids and tetraploids are self-compatible (C. S. Campbell et al. 1991; H. A. McAllister 2005). Some species have morphologically indistinguishable diploid and tetraploid races, with sexual and apomictic individuals. North American species are in need of biosystematic review.
Sorbus is treated here in the broad sense, as a provisional arrangement to accommodate more than 70 natural hybrids between simple- and pinnate-leaved subgenera (J. B. Phipps et al. 1990; E. B. Nelson-Jones et al. 2002; C. Kalkman 2004; A. Robertson et al. 2004, 2004b; J. J. Aldasoro et al. 2004, 2005). Additional hybrid taxa continue to be discovered in Europe (G. Aas et al. 1994; M. F. Fay et al. 2002; T. C. G. Rich and L. Houston 2006; A. Robertson and C. Sydes 2006). Nonetheless, the argument has been made to revive generic ranking for the simple-leaved subgenera Aria and Torminaria, based on flower and fruit characters (K. R. Robertson et al. 1991), with some support from molecular investigations (C. S. Campbell et al. 1995, 2007; D. Potter et al. 2007). Subgenus Torminaria is anomalous in Sorbus, having a unique flavonoid chemistry, leaves with relatively few broad lobes, and scented brown fruits, thick-skinned as in subg. Cormus (Spach) Duchartre and some Pyrus, and being dispersed by carnivorous mammals as well as birds (C. M. Herrera 1987, 1989). Eurasian hybrids between subgenera frequently involve S. torminalis of subg. Torminaria. Subgenera Aria and Torminaria are likely to be recognized at generic rank once molecular studies can consistently resolve their placement within the Pyrinae, overcoming current difficulties with interfertility, reticulate relationships, rapid radiation, and small samples (Campbell et al. 2007; Potter et al.).
Some species of Sorbus are cultivated as ornamentals. The colorful fruits of native and introduced species persist after the leaves drop and are consumed by birds across North America (A. C. Martin et al. 1951). One exotic species disseminated by birds is invasive (S. aucuparia). The pomes of S. americana, collected after a frost, can be sweetened for preserves. The pulp of some strains of S. aucuparia is reported to be less bitter. It may be eaten fresh or dried or used as flour. The fruits of a number of Eurasian species are made into vinegar, spirits, or medications. Sorbus domestica and S. torminalis pomes are sometimes eaten after being bletted (allowed to autodigest and become soft and mushy in texture). The fine-grained wood of Sorbus is used for carving or furniture in China. The bark of some species is antiseptic, or used to tan leather. Sorbus sambucifolia pomes show some potential in early testing for treating tumors (Y. Yoshizawa et al. 2000, 2000b).
In order to identify intergeneric hybrids involving Sorbus as one of the parents, the following key includes leads for ×Amelasorbus and ×Sorbaronia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 29, species 550–840+ (18 genera, 270 species, including 18 hybrids, in the flora).
The family name Malaceae Small (1903) is a conserved name, with Malus as its type genus. In contrast, the family name Pyraceae Vest (1818), with Pyrus as its type, is not a conserved name. Although Maleae was published later than Pyreae (1869), a Rosaceae tribe that includes both Malus and Pyrus is to be called Maleae (see Melbourne Code, Article 19.5, Example 5).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key to sub-genera of Sorbus
1. Leaves pinnately compound at least proximally, petiole nodes 5-lacunate; pome flesh without tanniferous cells. | subg. Sorbus |
1. Leaves simple, sometimes lobed, petiole nodes 3-lacunate; pome flesh with tanniferous cells. 5!-!Leaves simple, lobed, or proximally pinnately compound (escapes and hybrids). 14!-!Leaves pinnately compound (mostly native species) | → 6 |
2. Blade margins relatively deeply lobed; pome flesh composed entirely of tanniferous cells; styles connate 1/2 their lengths. | subg. Torminaria |
2. Blade margins entire, toothed, or relatively shallowly lobed; pome flesh with tanniferous cells in groups; styles distinct. | subg. Aria |
In order to identify intergeneric hybrids involving Sorbus as one of the parents, the following key includes leads for ×Amelasorbus and ×Sorbaronia.
1. Leaves simple, lobed, or proximally pinnately compound (escapes and hybrids). | → 2 |
1. Leaves pinnately compound (mostly native species). | → 6 |
2. Leaves simple, without leaflets; styles 2. | → 3 |
2. Leaves, at least some, proximally pinnate, with 1–3(–5) basal pairs of distinct leaflets; styles 2–5. | → 4 |
3. Leaves thinly hairy to glabrate abaxially, subpalmately lobed, lobes ± triangular, (1–)1.5–2.5 cm wide, apices acute to acuminate; pomes brown, narrowly obovoid, lenticels abundant; sepal margins prominently glandular (and villous), glands often relatively thick. | S. torminalis |
3. Leaves tomentose abaxially, proximally pinnately lobed, lobes ± oblong, 1–1.5(–1.8) cm wide, apices acute to obtuse; pomes bright red, ellipsoid, sometimes narrowly obovoid, lenticels few; sepal margins eglandular (and villous), rarely with inconspicuous glands. | S. intermedia |
4. Leaves tomentose abaxially; terminal leaflets 7–10-lobed; styles 2 or 3; pomes red. | S. hybrida |
4. Leaves glabrous, glabrate, or sparsely to densely villous abaxially; terminal leaflets 1–3-lobed; styles 3–5; pomes dark purple or red | → 5 |
5. Terminal leaflet coarsely serrate; pomes subglobose; sepals erect or spreading-ascending, prominent ×Amelasorbus | → 5 |
5. Terminal leaflet finely serrate; pomes ellipsoid to ovoid; sepals incurved, inconspicuous ×Sorbaronia | → 1 |
6. Leaflets shiny adaxially (visible on herbarium specimens with strong lighting), green to dark green, never glaucous or blue-green; w North America | → 7 |
6. Leaflets dull adaxially, green to blue-green or yellowish green, sometimes slightly glaucous; w, e North America | → 9 |
7. Pomes: sepals erect, prominent; flowering hypanthium plus sepals (4.5–)5–6 mm; petals white to pinkish; w Aleutians (Alaska). | S. sambucifolia |
7. Pomes: sepals incurved, inconspicuous; flowering hypanthium plus sepals 3–4 mm; petals white; w North America (except w Aleutians) | → 8 |
8. Indument primarily rufous on winter buds, leaflet axils, and inflorescences; fruiting pedicels essentially glabrous; leaflets 2.5–4.1(–4.5) cm. | S. californica |
8. Indument primarily whitish on winter buds, leaflet axils, and inflorescences; fruiting pedicels sparsely to densely villous; leaflets (3–)4–6.5(–8.7) cm. | S. scopulina |
9. Winter buds densely villous, hairs whitish, rarely rufous; hypanthia densely villous, hairs whitish. | S. aucuparia |
9. Winter buds glabrous or sparsely to densely villous, hairs primarily rufous; hypanthia glabrous or sparsely villous proximally, hairs whitish or rufous | → 10 |
10. Leaflet l/w ratios 3.4–5, apices gradually acuminate to long-acuminate; pomes 4–7 mm diam., not glaucous when fresh or dried. | S. americana |
10. Leaflet l/w ratios 1.9–3.5(–3.6), apices abruptly short-acuminate, cuspidate, or obtuse to acute; pomes (5–)7–13 mm diam., often glaucous (sometimes only when dried) | → 11 |
11. Winter buds glutinous, shiny; leaflets (11–)13–17; e North America. | S. decora |
11. Winter buds not glutinous, dull; leaflets 7–13; w North America. | S. sitchensis |
1. Leaf margins usually horny; carpels free; flowers: perianth and androecium perigynous;
fruits woody capsules surrounded by a hypanthium, splitting into 5 follicles; seeds winged | Vauquelinia |
1. Leaf margins not horny; carpels ± adnate to hypanthium; flowers: perianth and androecium epigynous; fruits pomes; seeds not winged or pyrenes. | → 2 |
2. Fruiting carpels woody or bony. | → 3 |
3. Leaf margins entire; stipules short-adnate to petiole; stems unarmed; sepals erect in
flower; petal base clawed. | Cotoneaster |
3. Leaf margins ± serrate, crenate, serrulate, or crenulate, sometimes entire; stipules free; stems usually armed (sometimes with compound thorns), sometimes unarmed; sepals spreading in flower; petal base slightly or barely clawed. | → 4 |
4. Leaves persistent or late-deciduous; flowers 3–10(–12) mm diam., hypanthium campanulate; pomes 3–8 mm diam. | Pyracantha |
4. Leaves deciduous (sometimes winter-persistent in south); flowers 8–35 mm
diam., hypanthium ± obconic; pomes 6–40 mm diam. | → 5 |
5. Flowers 8–25 mm diam., stamens 5–20 (rarely 30–45); pomes yellow to red or purplish to black mature, 6–20(–25) mm diam.; pyrenes 1–5; short shoots present; inflorescences 1–50-flowered, domed panicles, corymbose, or flowers solitary. | Crataegus |
5. Flowers 25–35 mm diam., stamens 25–35(–40); pomes brownish, 15–40 mm diam.; pyrenes 5; short shoots rare or absent; inflorescences 1(or 2) flowered | Mespilus |
2. Fruiting carpels cartilaginous. | → 6 |
6. Stems armed (thorns present).> | → 7 |
7. Stipules persistent; pedicels short or absent; styles basally connate 1/3 of length;
pome flesh without stones; stamens 40–60; fruiting sepals deciduous. | Chaenomeles |
7. Stipules usually deciduous or caducous; pedicels present; styles distinct or basally
connate; pome flesh with stones (at least near carpels and epidermis); stamens 15–50;
fruiting sepals persistent or deciduous. | → 8 |
8. Pome flesh with stone cells adjacent to carpels and epidermis; styles basally
connate. | Malus |
8. Pome flesh with abundant stone or grit cells; styles distinct. | Pyrus |
6. Stems unarmed. | → 9 |
9. Inflorescences: flowers solitary or 1–5-flowered, corymbs or cymes. | → 10 |
10. Pomes yellow; ovules (seeds) many; inflorescences: flowers solitary. | → 11 |
11. Leaf margins entire, abaxial surfaces densely villous; buds ovoid, apices obtuse or acuminate, tomentose; young branches tomentose, glabrescent; stipules caducous; flowers 40–50 mm diam., petals white or light pink, suborbiculate, ovate, or obovate, stamens equal to or slightly longer than petals; pomes pyriform or subglobose, 30–50 mm. | Cydonia |
10. Pomes pink, yellow-orange, purple, purplish or bluish black, brownish, or nearly black; ovules (seeds) (1 or)2; inflorescences 1–5-flowered, cymes or corymbs. | → 12 |
12. Pomes yellow-orange; stipules adnate to petiole and base of blade; petioles short or absent; leaf blades elliptic to oblanceolate or linear. | Peraphyllum |
12. Pomes pink, bluish or purplish black, purple, brownish, or nearly black; stipules free; petioles present; leaf blades elliptic, elliptic-oblong, or oblong-ovate to orbiculate. | → 13 |
13. Leaves leathery, drought-deciduous or persistent; sepals nearly orbiculate (inner broadly deltate), petals round or kidney-shaped; carpels barely connate or distinct, styles lateral; pomes translucent, vivid pink, drying purplish black. | Malacomeles |
13. Leaves membranous to coriaceous (not leathery), deciduous; sepals triangular to lanceolate, petals linear to orbiculate; carpels connate, styles terminal; pomes bluish or purplish to nearly black, pinkish or maroon-purple, dark purple-blue, or brownish. | Amelanchier |
9. Inflorescences (4 or)5–400+-flowered, panicles, sometimes racemes, corymbs, or
subumbellate. | → 14 |
14. Leaves persistent, leathery; carpels basally adnate to hypanthium. | → 15 |
15. Leaf margins flat; flowers 15–20 mm diam.; pedicels short or nearly absent; hypanthia usually tomentose; stamens 20; carpels connate, styles (2–)5; pomes soft apricot yellow, 20–30 mm (diam.). | Eriobotrya |
15. Leaf margins revolute; flowers 10 mm diam.; pedicels present; hypanthia glabrous or weakly floccose; stamens 10; carpels distinct, styles 2 or 3; pomes usually bright red, sometimes yellow, 5–10 mm | Heteromeles |
14. Leaves usually deciduous, sometimes semipersistent or persistent (then margin entire), membranous to ± leathery; carpels adnate to all or 1/3–1/2 of hypanthium. | → 16 |
16. Pome flesh with stones or sclereids. | → 17 |
17. Inflorescences terminal, 6–400+-flowered flat-topped or rounded panicles; flowers opening after leaf expansion, 5–17 mm diam.; sepals erect or ascending; leaves pinnately divided, sometimes simple or lobed. | Sorbus |
17. Inflorescences terminal on short shoots, 4–9-flowered racemes or simple corymbs, umbel-like; flowers developing with or before leaves, 15–45 mm diam.; sepals reflexed; leaves simple. | Pyrus |
16. Pome flesh without stones. | → 18 |
18. Stipules adnate to petiole, persistent | Aronia |
18. Stipules free, caducous or deciduous. | → 19 |
19. Leaves persistent or deciduous; inflorescences corymbose or subumbellate; pomes red or black. | Photinia |
19. Leaves deciduous; inflorescences racemes; pomes bluish or purplish to nearly
black, pinkish or maroon-purple, dark purple-blue, or brownish | Amelanchier |
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