|Sorbus subsp. var.||Mountain ash|
Sorbus is a genus of about 100–200 species of trees and shrubs in the subfamily Maloideae of the Rose family Rosaceae. Species of Sorbus (s.l.) are commonly known as whitebeam, rowan, service tree, and mountain ash. The exact number of species is disputed depending on the circumscription of the genus, and also due to the number of apomictic microspecies, which some treat as distinct species but others group in a smaller number of variable species. Recent treatments  treat Sorbus in a narrower sense to include only the pinnate leaved species of subgenus Sorbus, raising several of the other subgenera to generic rank.
Sorbus is unrelated to the true ash trees which belong to the genus Fraxinus, although the leaves are superficially similar.
|Standard Cyclopedia of Horticulture|
Sorbus (ancient Latin name of S. domestica). Including Aria, Cormus, Micromeles, and Torminaria. Rosaceae. Ornamental woody plants grown for their handsome foliage, attractive white flowers and ornamental usually red fruit.
Deciduous trees or shrubs: lvs. alternate, stipulate, simple and serrate or odd-pinnate, folded or rarely convolute in the bud: fls. in compound corymbs; sepals and petals 5; stamens 15-20, with red or yellow anthers; carpels 2-5, either partly free above and half superior or wholly connate and quite inferior; styles free or connate at the base: fr. a 2-5-loculed pome, usually rather small; the cells with cartilaginous or leathery walls, each with 1 or 2 seeds. Closely allied and often referred to Pyrus, from which it is chiefly distinguished by its compound infl. and by the fls. being in most species more or less perigynous; the frs. are usually smaller and berry-like.—About 80 species distributed throughout the northern hemisphere, in N. Amer., south to N. C. and New Mex., in Asia south to the Himalayas. The frs. of some species, as S. domestica, S. torminalis, S. Aucuparia var. dulcis and var. rossica are edible and are made into preserves in Europe; the strong and close-grained wood of S. torminalis and S. domestica is used for handles of tools and for similar small articles.
The sorbuses are handsome trees or shrubs with graceful pinnate or with simple foliage sometimes silvery white beneath, and with showy clusters of small white rarely pinkish flowers in spring, followed by red or rarely whitish or brown fruits usually berry-like, rarely larger and apple- or pear-shaped. Most of the pinnate-leaved kinds are hardy North except some Asiatic species and S. domestica, which seem tender north of Massachusetts; they are chiefly inhabitants of mountainous regions, and the northern species, as S. americana and S. decora, do not thrive well in warmer and drier climates, while the simple-leaved species, as S. alnifolia, S. intermedia, S. Aria, and S. torminalis, endure drought and heat well and have proved hardy at least as far north as Massachusetts. The trees are often attacked by borers. Propagation is by seeds sown in fall or stratified, also by layers. Varieties and rarer kinds are usually budded or grafted on allied species, but most kinds will grow on S. Aucuparia or S. americana and on hawthorn. They all have handsome foliage, which usually turns orange-red in fall; their fruits are showy and often remain on the branches the whole winter if not eaten by birds. They are not particular as to the soil and are well suited for planting on rocky hillsides. Those of the Aucuparia group are more adapted for cool and moist mountain regions; those of the Aria and Torminaria group, which grow especially well on limestone soil, are suited to warmer and drier climates. S. hybrida is sometimes used as a small-sized avenue tree on account of its regular pyramidal habit. CH
Pests and diseases
As treated in its broad sense, the genus is divided into two main and three or four small subgenera (with more recent generic assignments in parentheses):
- Sorbus subgenus Sorbus (genus Sorbus s.s.), commonly known as the rowan (primarily in the UK) or mountain ash (in both North America and the UK), with compound leaves usually hairless or thinly hairy below; fruit carpels not fused; type species Sorbus aucuparia (European rowan). Distribution: cool-temperate Northern Hemisphere. (Genus Sorbus s.s.)
- Sorbus subgenus Aria (genus Aria), the whitebeam, with simple leaves usually strongly white-hairy below (hence the name, from German Weissbaum, 'white tree'); fruit carpels not fused; type species Sorbus aria (common whitebeam). Distribution: temperate Europe & Asia.
- Sorbus subgenus Cormus (genus Cormus), with compound leaves similar to subgenus Sorbus, but with distinct fused carpels in the fruit; just one species, Sorbus domestica (True Service Tree). Distribution: North Africa, warm-temperate Europe, West Asia.
- Sorbus subgenus Torminaria (genus Torminalis), with rather maple-like lobed leaves with pointed lobes; fruit carpels not fused; just one species, Sorbus torminalis (Wild Service Tree). Distribution: temperate Europe, south to the mountains of North Africa and east to the Caucasus ranges.
- Sorbus subgenus Chamaemespilus (genus Chamaemespilus), a single shrubby species Sorbus chamaemespilus (false medlar) with simple, glabrous leaves and pink flowers with erect sepals and petals. Distribution: mountains of southern Europe.
- Hybrids are common in the genus, including many between the subgenera; very often these hybrids are apomictic (self-fertile without pollination), so able to reproduce clonally from seed without any variation. This has led to a very large number of microspecies, particularly in western Europe (including Britain) and parts of China.
|Standard Cyclopedia of Horticulture|
S. aperta, Koehne. Allied to S. Aucuparia. Tree, to 40 ft.: lfts 9-17, elliptic to elliptic-oblong, acute, serrate, glabrous, 1-2 in. long: styles 5: fr. small, whitish. W. China.—S. arbutifolia, Heynh.—Aronia arbutifolia.—S. Chamaemespilus, Crantz (Pyrus Chamaemespilus, Poll. P. alpina, Dur. Aria Chamaemespilus, Host.). Upright shrub, 6 ft. high, allied to S. Aria. Lvs. elliptic to oblong, serrate, almost glabrous, 1 1/2 – 2 1/2 in. long: fls. pinkish, with upright petals, in dense corymbs about 1 1/2 in. broad: fr. oval, orange to brownish red. Cent. and S. Eu. H.W. 3, p. 84. Var. sudetica, Wenzig. Lvs. whitish or grayish tomentose beneath. Mountains of Cent. Eu.—S. commixta, Hedl. (S. Aucuparia var. japonica, Maxim. S. japonica, Koehne, not Hedl.). Allied to S. americana. Small tree: lfts. 11-15, oblong-lanceolate to lanceolate, long-acuminate, glabrous, 2-3 in. long: infl. glabrous: fr. red, small. Japan. S.I.F. 2:31.—S. Conradinae, Koehne. Allied to S. Aucuparia. Tree, to 25 ft.: stipules large, persistent; lfts. 11-13, oblong to oblong-lanceolate, short-acuminate, serrate, tomentose beneath, 2-3 in. long: styles usually 4: fr. globose, red, about 1/3 in. across. W.China.—S. cuspidata, Hedl. (S. vestita, Schau. Pyrus yestita, Wall. Pyrus crenata, Lindl., not Don. Cormus lanata, Koehne. S. nepalensis, Hort.). Tree, allied to S. Aria: lvs. elliptic to elliptic-oblong, acuminate, doubly serrate, densely tomentose beneath, 3-7 in. long: styles usually 5, woolly at the base: fr. about 1/2 in. across. Himalayas. G.C. II. 1:17. B.M. 8259.—S. Decaisneana, Rehd. (Micromeles Decaisneana, Schneid.). Tree, to 40 ft.: lvs. elliptic-obovate, crenate-serrulate, with 8-10 pairs of veins, nearly glabrous beneath, 2-3 1/2 in. long: infl. tomentose, 1 1/2 in. across; styles usually 3, connate below: fr. ovoid, red, 1/3 in. across with deciduous calyx. Cent. and W.China.—S. discolor, Hedl. (Pyrus discolor, Maxim.). Doubtful species allied to S. Aucuparia; possibly the same as S. pekinensis. The plants in cult. as S. discolor probably do not belong here. —S. Esserteauiana, Koehne. Allied to S. Aucuparia. Tree, to 25 ft.: stipules large, persistent; lfts. 11-13, oblong-lanceolate, subacuminate, serrate, whitish tomentose beneath, 1 1/2 – 3 1/2 in. long: infl. tomentose, 4-6 in. across: fr. globose, scarlet, 1/3 in. across. W. China.—S. gracilis, Koch (Pyrus gracilis, Sieb. & Zucc.). Shrub, with pinnate lvs., those at the base of the loose, few-fld, corymbs with large, incised-dentate stipules: lfts. 7-9, ovate to ovate-oblong, 1-1 1/2 in. long: styles 2. Cent. and S. Japan.—S. Hostii, Koch (Pyrus Hostii, Hemsl. Aria Hostii, Jacq. f.). Supposed to be a hybrid between S. Mougeotii and S. Chamaemespilus: shrub or small tree, 12 ft. high: lvs. oval to elliptic-obovate, sharply serrate: fls. pinkish, in dense corymbs about 2 1/2 in. broad: fr. globose, ovoid, red. Mountains of Cent. Eu. Gn. 20:376. R.H. 1877:210.—S. japonica. Hedl. (Micromeles japonica, Koehne. S. Koehnei, Zabel). Allied to S. alnifolia. Lvs. pubescent above, grayish tomentose beneath: infl. denser with smaller fls.: fr. deeper scarlet, punctate. Japan. S.I.F. 1:48.—S. japonica, Koehne –S. commixta.—S. japonica, Zabel-Eriobotrya japonica.—S. Koehnei, Zabel (not to be confused with S. Koehneana, Schneid., a species of the Aucuparia group, not in cult.)-S. japonica.—S. lanata, Wenzig (Pyrus lanata, Don). Tree, allied to S. Aria: lvs. oval, sharply and doubly serrate and slightly lobed, 4-7 in. long: styles 2-3, connate below, woolly: fr. globose, 1/2 – 1 1/2 in. across. Himalayas. –S. Matsumurana, Koehne (Pyrus Matsumurana, Makino). Allied to S. decora. Shrub, glabrus: lfts. 9-13, oblong-ovate to oblong, acute, serrate above the middle, 1 1/2 – 2 1/2 in. long: stamens half as long as petals; styles 5: fr. red, 1/3 in., bloomy. Japan. -S. megalocarpa, Rehd. Shrubby tree, to 25 ft.: lvs. elliptic-obovate to obovate-oblong, acuminate, crenate-serrate, glabrous, 5-10 in. long: infl. 4-6 in. across: styles usually 3: fr. 1/2-l in. long, russet-brown. W.China.— S. meliosmifolia, Rehd. Allied to S. alnifolia. Tree, to 30 ft.: lvs. short-petioled, ovate to elliptic-oblong, doubly serrate, with 18-24 pairs of veins, slightly pubescent beneath, 5-8 in. long: infl. 2-4 in. across: fr. subglobose, brownish red, 1/2 in. long. W. China.—S. Mougeotii, Soyer-Willemet (Pyrus Mougeotii, Aschers. & Graebn.). Allied to S. intermedia: often shrubby: lvs. ovate to ovate-oblong, lobed, short-acuminate, with 8-12 pairs of veins: fr. red, globose, 1/2 in. across, edible. Mountains of Cent. Eu. H.W. 3, p. 83,—S. nepalensis, Hort.-S. cuspidata.-S. occidentalis, Greene -S. pumila.—S. ochrocarpa, Rehd. Allied to S. Aria. Lvs. generally elliptic, doubly denticulate-serrate, grayish tomentose beneath, 2-4 in. long: infl. small, sessile, styles 2, connate at base: fr. pale, sub-globose, 1/4 in. across. W. China.—S. pekinensis, Koehne. Allied to S. americana. Tree, nearly glabrous: lfts. 13-17, oblong, acute, serrate, 1 1/2- 2 1/2 in. long: infl. 4-8 in. across; styles 3: fr. subglobose, small, pinkish white or yellowish. N.China. Gt. 55:1551, fig. 7.— S. pohuashanensis, Hedl. Allied to S. Aucuparia. Tree: stipules large, persistent; lfts. 13-15, ovate-oblong to ovate-lanceolate, whitish beneath, 1 1/2-2 in. long: infl. 4-5 in. across, tomentose: fr. red, subglobose, 1/3 in. across. N. China.—S. pumila, Raf. (S. sitchensis, Roem. S. occidentalis, Greene. S. sambucifolia var. Grayi, Wenzig). Allied to S. decora. Shrub: lfts. 7-11, oval to oval-oblong, obtuse, serrate toward the apex, bluish green, 1-2 in. long: infl. 1-3 in. across; styles 3-5: fr. subglobose, red. Alaska to N. Calif. G.F. 10:85.—S. sambucifolia, Roem. Allied to S. americana. Shrub: lfts. 9-11, ovate-oblong, acuminate, serrate, glabrous, green on both sides, 2-3 in. long: infl. slightly villous: fr. subglobose, 1/2 in. across, yellowish red. N. E. Asia. Very rare in cult., usually S. decora is cult. under this name.—S. Sargentiana, Koehne. Allied to S. Aucuparia. Tree, to 30 ft.: stipules large, persistent: lfts. 9-11, oblong-lanceolate, acuminate, serrate, villous beneath while young; infl. 6 in. across; styles 3-5: fr. globose, 1/4 in. across, scarlet. W. China. Not to be confused with S. Sargentii which see under No. 8. —S. scalaris, Koehne. Allied to S. Vilmorinii. Shrub, to 20 ft.: stipules large, persistent; rachis slightly winged: lfts. 25-27, linear-oblong, dentate only at the apex, villous beneath, 3/4 – 1 1/2 in. long: infl. tomentose; styles 3-4: fr. globose, red, 1/3 in. across. W. China. —S. setuchwanensis, Koehne. Allied to S. Vilmorinii. Shrub, to 15 ft.: rachis slightly winged: lfts. 25-35, narrow-oblong, serrulate, glabrous, 1/5 – 1/2 in. long: infl. glabrous, l-2 1/2 in. across; styles 2-4: fr. globose, 1/4 in. across, whitish or pale purple. W. China. –S. sitchensis, Roem. –S.pumila. –S. sudetica, Heynh. –S. Chamaemespilus var sudetica. –S.unguiculata, Koehne. Allied to S.Vilmorinii. Shrub, to 15 ft.: rachis narrowly winged: lfts. 23-33, oval to narrow-oblong, serrulate, villous on midrib beneath, 1/3 – 3/4 in. long: infl. 1-2 in. broad, slightly villous; claw or petals one-half as long as blade: fr. globose, 1/3 in. across, whitish or pale purple. W. China.-S.vestita, Wall.-S.cuspidata. CH
- ↑ Robertson, K. R., J. B. Phipps, J. R. Rohrer, and P. G. Smith. 1991. A Synopsis of Genera in Maloideae (Rosaceae). Systematic Botany 16: 376–394.
- ↑ McAllister, H. 2005. The Genus Sorbus: Mountain Ash and Other Rowans. Richmond, Surrey, UK: Royal Botanic Gardens, Kew.
- ↑ Cite error: Invalid
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- ↑ Campbell C. S., R. C. Evans, D. R. Morgan, T. A. Dickinson, and M. P. Arsenault. 2007. Phylogeny of subtribe Pyrinae (formerly the Maloideae, Rosaceae): Limited resolution of a complex evolutionary history. Pl. Syst. Evol. 266: 119–145.