Sorbus aucuparia, commonly called rowan (, also ) and mountain-ash, is a species of deciduous tree or shrub in the rose family.
The tree has a slender trunk with smooth bark, a loose and roundish crown, and its leaves are pinnate in pairs of leaflets on a central vein with a terminal leaflet. It flowers from May to June in dense corymbs of small creamy-white flowers and develops small red pomes as fruit that ripen from August to October and are eaten by many bird species.
It is a highly variable species, and botanists have used different definitions of the species to include or exclude trees native to certain areas. A recent definition includes trees native to most of Europe and parts of Asia, as well as northern Africa. The range extends from Madeira, the British Isles and Iceland to Russia and northern China. Unlike many plants with similar distributions, it is not native to Japan. The plant is frost hardy and colonises disrupted and inaccessible places as a short-lived pioneer species.
The fruit and foliage have been used in the creation of dishes and beverages, as a folk medicine, and as fodder for livestock. Its tough and flexible wood has traditionally been used for woodworking. It is planted to fortify soil in mountain regions or as an ornamental tree and has several cultivars.
Description Sorbus aucuparia is a small tree or shrub that typically grows to between about in height, occasionally to , and exceptionally to .Schauer 2001, p. 342 The crown is loose and roundish or irregularly shaped but wide and the plant often grows multiple trunks.Zauner 2000, p. 52Harz 2009, p. 72 A trunk is slender and cylindrical and reaches up to in diameter, and the branches stick out and are slanted upwards.Erlbeck, Haseder, Stinglwagner 1998, p. 166 The bark of a young plant is yellowish grey and gleaming and becomes grey-black with lengthwise cracks in advanced age; it descales in small flakes.Godet 1994, p. 52 Lenticels in the bark are elongated and coloured a bright ochre.Godet 2008, p. 110 The plant does not often grow older than 80 years in warmer regions and is one of the shortest-lived trees in temperate climate,Laudert 1999, p. 57 but can occasionally live longer, to 150 years. The wood has a wide reddish white sapwood and a light brown to reddish brown heartwood. It is diffuse-porous, flexible, elastic, and tough, but not durable, with a density of in a dried state. The roots grow wide and deep, and the plant is capable of root sprouting and can regenerate after coppicing.
The compound leaves are pinnate with four to nine pairs of leaflets on either side of a terete central vein and with a terminal leaflet. The leaves are up to long, wide. They have paired leaf-like stipules at the base of the petiole, and are arranged alternately along a branch, distinguishing them from those of ash, Fraxinus excelsior, which are opposite and without stipules. The leaflets are elongated-lanceolate in shape, long, and wide with a sharply serrated edge, and have short stems or sit close to the central vein except for the outermost leaflet.Godet 1994, p. 138 The leaflets are covered in grey-silvery hairs after sprouting but become mostly bare after they unfold.Reichholf, Steinbach 1992, p. 103 Their upper side is dark green and their underside is a greyish green and thinly hairy. Young leaflets smell like marzipan when brayed.Hecker 1995, p. 130 The leaflets are asymmetrical at the bottom. The foliage grows in May and turns yellow in autumn or a dark red in dry locations.Smolik 1996, p. 63
The buds are often longer than and have flossy to felted hairs. These hairs, which disappear over time, cover dark brown to black bud scales. The terminal buds are oval and pointed and larger than axillary buds, which are narrow, oval and pointed, close to the twig, and often curved towards it.
The species is monoecious. It reaches maturity at age 10 and carries ample fruit almost every year. The plant flowers from May to June (on occasion again in September) in many yellowish white corymbs that contain about 250 flowers.Kremer 2010, p. 42Raspé, Findlay, Jacquemart 2000, p. 910 The corymbs are large, upright, and bulging.Godet 1998, p. 68 The flowers are between in diameter and have five small, yellowish green, and triangular sepals that are covered in hairs or bare. The five round or oval petals are yellowish white and the flower has up to 25 stamens fused with the corolla to form a hypanthium and an ovary with two to five styles; the style is fused with the receptacle. The flowers have an unpleasant trimethylamine smell. Their nectar is high in fructose and glucose.
Its berries are round pomes between in diameter that ripen from August to October. The fruit are green before they ripen and then typically turn to orange or scarlet when ripe. The sepals persist as a black, five-pointed star on the ripe fruit.Erlbeck, Haseder, Stinglwagner 1998, p. 167 A corymb carries 80 to 100 pomes.Garcke 1972, p. 722 A pome contains a star-shaped ovary with two to five locules each containing one or two flat, narrow, and pointed reddish seeds. The flesh of the fruit contains carotenoids, citric acid, malic acid, parasorbic acid, pectin, provitamin A, sorbitol, tannin, and vitamin C. The seeds contain glycoside.Hensel 2007, p. 112 Its fruit persists for an average of 100.6 days, and bears an average of 2.5 seeds per fruit. Fruits average 73.0% water, and their dry weight includes 8.9% carbohydrates and 3.1% lipids.
The species has a chromosome number of 2n=34.Raspé, Findlay, Jacquemart 2000, p. 916
Taxonomy
Fossil record Fossils of Sorbus aucuparia have been described from the fossil flora of Kızılcahamam district in Turkey, which is of early Pliocene age.
Names
The binomial name Sorbus aucuparia is composed of the Latin words for service tree and , which derives from the words for "bird" and for "catching" and describes the use of the fruit of S. aucuparia as bait for fowling. The plant is most commonly known as rowan, and has also been called European rowan, mountain-ash, European mountain-ash, quick beam, quickbeam, or rowan-berry. The names rowan and mountain ash may be applied to other species in Sorbus subgenus Sorbus, and mountain ash may be used for several other distantly related trees. The species is not closely related to either the true ash trees (genus Fraxinus), which also carry pinnate leaves, or the species Eucalyptus regnans, also called mountain ash, native to Tasmania and Victoria in southeastern Australia.Breckwoldt 2011, p. 152
The common name mountain ash dates from the 16th century. It was first used by John Gerard in 1597, translating it directly from the then botanists' Latin Montana fraxinus Grigson G. 1974. A Dictionary of English Plant Names. Allen Lane
S. aucuparia was previously classified as Pyrus aucuparia.Hora 1993, p. 184 Distribution and habitat
Sorbus aucuparia is found in five subspecies:Raspé, Findlay, Jacquemart 2000, p. 911 Sorbus aucuparia subsp. aucuparia: found in most of the species' range, less in the South Sorbus aucuparia subsp. fenenkiana (Georgiev & Stoj.): has thin, sparsely hairy leaflets and depressed-globose fruit, restricted to Bulgaria Sorbus aucuparia subsp. glabrata (Wimm. & Grab.): less hairy, found in Northern Europe and Central European mountains Sorbus aucuparia subsp. praemorsa (Guss.): has hairy leaflets and ovoid fruit, found in Southern Italy, Sicily, and Corsica Sorbus aucuparia subsp. sibirica (Hedl.): nearly hairless, found in North Eastern Russia
It can be found in almost all of Europe and the Caucasus up to Northern Russia and Siberia, but it is not native to Southern Spain, Southern Greece, Sardinia, the Balearic Islands, the Azores, and the Faroe Islands.Větvička 1995, p. 200 The species was introduced as an ornamental species in North America. It is widespread from plains to mountains up to the tree line where it grows as the only deciduous tree species among krummholz. In the Alps it grows at elevations of up to . S. aucuparia appears north of the boreal forest at the arctic tree line; in Norway, it is found up to the 71st parallel north. It has naturalised in America from Washington to Alaska and eastward in Canada and the northeast of the US very successfully.
S. aucuparia is an undemanding species and can withstand shade. It is frost hardy and can tolerate winter dryness and a brief growing season.Raspé, Findlay, Jacquemart 2000, p. 915 The plant is also resistant to air pollution, wind, and snow pressure.Laudert 1999, p. 80Laudert 1999, p. 83 It mostly grows on soil that is moderately dry to moderately damp, acidic, low on nutrients, sandy, and loose.Godet 2008, p. 378 It often grows in stony soil or clay soil, but also sandy soil or wet peat. The plant grows best on fresh, loose, and fertile soil, prefers average humidity, and does not tolerate saline soil or waterlogging.Aichele, Golte-Bechtle 1997, p. 78 It can be found in light woodland of all kinds and as a pioneer species over fallen dead trees or in clearcuttings, and at the edge of forests or at the sides of roads. The seeds germinate easily, so the plant may appear on inaccessible rock, ruins, branch forks, or on hollow trees.
The tallest S. aucuparia in the United Kingdom stands in the Chiltern Hills in South East England. This exceptional specimen is tall and has a trunk diameter of . The stoutest is in the Scottish Highlands near Kingussie, with a girth of 4.31 m (approximately 1.37 m diameter); another near Stapleton in Herefordshire is almost as stout at 4.29 m girth. In Germany, an unusually large specimen is located near Wendisch Waren, a village in Mecklenburg-Vorpommern. This tree stands at more than tall, is around 100 years old, and has a diameter of .Ullrich, Kühn, Kühn 2009, p. 29 The tallest known specimen in Ireland is an tall specimen at Glenstal Abbey, County Limerick.
Ecology
The species is pollinated by bees and flies. Its seeds are not digested by birds and are thus propagated by being passed intact in their droppings.Lohmann 2005, p. 60 The fruit are eaten by about 60 bird species and several mammals.Laudert 1999, p. 81 They are liked particularly by thrushes and other songbirds, and are also eaten by cloven-hoofed mammals (deer, sheep, cattle), red fox, European badger, dormouse, and squirrel. The fruit are eaten by frugivorous birds from late summer to winter, including Bohemian waxwing, blackbirds, fieldfare, and redwing. Cloven-hoofed mammals may also browse the foliage and bark excessively. The plant roots can be found in symbiosis with arbuscular mycorrhizal and less commonly with ectomycorrhizal fungi.
It is usually later superseded by larger forest trees.Lohmann 2005, p. 61 In Central Europe it often grows in association with red-berried elder, goat willow, Eurasian aspen, and silver birch. The plant is fire-intolerant and tends not to accumulate plant litter.Raspé, Findlay, Jacquemart 2000, p. 913
Other species of the genus Sorbus, and also species in the related genus Aria, readily hybridise with S. aucuparia and hybrid speciation can result. Plants of hybrid origin between these two genera are now classified in the genus Hedlundia, and include Hedlundia hybrida, a small tree with oval serrated leaves and two to three pairs of leaflets, which is a hybrid with Hedlundia intermedia, and Hedlundia thuringiaca, a medium-size tree with elongated leaves and one to three pairs of leaflets that are sometimes fused at the central vein, which is a hybrid with Aria edulis.Hora 1993, p. 185–186