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Sorbus aucuparia L., Rowan

Account Summary

Native, common, sometimes planted. Eurasian boreo-temperate.

1882; Stewart, S.A.; Fermanagh.

Throughout the year.

Growth form and preferred habitats

Rowan or Mountain Ash, Sorbus aucuparia is the commonest member of a large genus, occurring not only native and wild, but also as an ornamental garden subject. While decidedly variable, five subspecies being distinguished in Europe (Tutin et al. 1968, 2), the typical form, subsp. aucuparia, which occurs throughout B & I, grows to a slender medium-sized tree around 20 m in height, with a narrow crown and erect or somewhat spreading branches and pinnate leaves. As the English common name suggests, Mountain Ash is a tree particularly associated with higher ground in areas of greater rainfall and it is much more local in drier, lowlands areas and in the agricultural midlands of B & I (Rackham 1980; Rich et al. 2010). Typical habitats include deciduous woods in upland areas or in river gorges, open heaths, bracken-covered hillsides, cliffs and rocky hillsides. The small, bright scarlet fruits, although sour and bitter tasting, attract many bird species so that seeds can be bird-sown anywhere, including on waste ground, along hedges and on roadside and railway banks (Rich et al. 2010). The specific epithet 'aucuparia' is from the Latin 'aucupatorius', meaning 'used for catching birds' ('avis', bird and 'capio', catch), indicating that fowlers used the fruit as lures or bait (Gilbert-Carter 1964).

In woodland, Rowan prefers open illumination or semi-shade situations that allow it to freely flower and fruit successfully. It reproduces entirely by seed and cannot survive in the longer term beneath a dark, heavy, deciduous tree canopy like oak. Seed transported into woods by birds and other berry-eating animals may allow some seedlings and saplings to develop in shade and they may persist there for long periods but fail to flower and fruit. This is why S. aucuparia does best on steeper, upland slopes and glens, where shallow, rocky, leached soils prevent taller dominant tree species forming a complete or heavy canopy. The more open, partial canopy on slopes allows shorter lived, rapidly developing trees like Rowan and the even more light-demanding Birch to thrive and form a secondary canopy layer, or even to dominate canopy gaps in deciduous broadleaved woods for short periods. The species is described as a stress-tolerant competitor and it is not long-lived, having a maximum lifespan of about 150 years (Grime et al. 1988).

S. aucuparia tends to avoid calcareous and heavy soils, but it can occur on calcareous ground where there is sufficient depth of overlying peat or litter to produce the dry to damp but well-drained, low-nutrient, at least slightly acidic soil conditions that this small to medium-sized tree requires to compete with its neighbours. It is probably most frequent on soils below pH 5.5, the mean acidity of most agricultural soils (Grime et al. 1988).

Rowan can tolerate remarkably exposed conditions on cliffs and steep moorland slopes where it can avoid grazing and the encroachment of blanket peat. Often, in such situations, it becomes reduced in scale to a small tree, or dwarfed further to shrub size. In other areas of Britain and Ireland, with higher mountains than Fermanagh, it grows as isolated shrubby trees on cliffs inaccessible to grazing animals up to around 650 m in Britain. Occasionally it occurs above this altitude, up to as much as 900 m, as stunted saplings, a feature that makes it the highest growing tree species in these islands (Grime et al. 1988; Raspé et al. 2000).

Flowering reproduction

S. aucuparia is a sexual diploid. The ± flat-topped inflorescence is a densely packed compound corymb of between 120-250 small, 8-10 mm diameter, 5-merous flowers each with c 20 stamens. The inflorescence is heavily scented (Sell & Murrell (2014) describe it as "sweet and sickly") and the nectar is partially concealed, being secreted by the ring of the hypanthium between the stamens and the carpel bases. In warm weather, the stamens spread apart to expose the nectar, but in dull conditions they converge, conceal and protect it (Thomas 2000).

The extremely numerous flowers are self-incompatible, protogynous, outbreeders, pollinated in May and early June by flies, bees, wasps, moths and a wide variety of other insects (Raspe et al. 2000). Not all flowers set fruit: the proportion doing so in W Scotland can be as low as 16% (Doar 1989, quoted by Rich et al. 2010). The fruit is a 2- to 5-celled, berry-like pome, 6-9 mm in diameter, each cell containing one or two small, brown seeds. Seed bearing does not begin until the tree is about 15 years old (Raspé et al. 2000).

The species is well adapted to the short growing seasons that prevail at both high altitudes and high latitudes and, in Fermanagh, all the fruits are fully ripe and ready for bird- or mammal-dispersal by mid August or earlier. A good fruit crop is produced virtually every year, but in our mild, damp climate, uncollected fruits deteriorate fairly rapidly. Seed requires chilling to break deep dormancy and only one of seven publications suggested that seed is more than transient in the soil (Thompson et al. 1997).

Fermanagh occurrence

Mountain Ash or Rowan forms a significant part of Fermanagh's upland woody flora, being found in a wide variety of habitats throughout the VC at all levels. It is very widespread throughout the county and has been recorded in 327 tetrads, 61.9% of those in the VC. Although in Fermanagh it is most typically found in damp upland acidic woods, rocky glens and scrubby hillsides, whenever it is protected from heavy grazing pressure, Rowan can also feature in areas of calcareous terrain, including lowland lakeshores and on upland cliffs, eg at Knockmore Hill and at Hanging Rock NR.

British and Irish occurrence

S. aucuparia is common and widespread throughout most of B & I, but becomes more scarce in lowland S & E England and in the Irish Midland plain, probably due to the predominance of near-neutral, base-rich soils of these areas, in which the tree is a poor competitor (Grime et al. 1988; Raspé et al. 2000; Preston et al. 2002). In some of its lowland E & C England stations it is probably not native, but derived from planted material (Raspé et al. 2000).

European and world occurrence

In Europe, the distribution of S. aucuparia appears limited by high temperature induced water stress, although another view is that a combination of poor drought tolerance, adaptation to a short early growing season and a cold requirement for bud burst, may be the main determining factors (Raspé et al. 2000). S. aucuparia subsp. aucuparia occurs throughout most of Europe from S Scandinavia and S Russia (although not in their Arctic regions), south to the mountains of C Spain and Portugal, Corsica, Italy, Macedonia and the Caucasus. In the northern regions of Iceland, Scandinavia, Russia and in the mountains of C Europe it is replaced by subsp. glabrata (Wimmer & Grab.) Cajander.

S. aucuparia is absent only from the Azores, the Faeroes, Spitsbergen, Balearic Isles, Sardinia, Crete and Turkey (Raspé et al. 2000; Hultén & Fries 1986, Map 1158).

Uses

All parts of the Rowan tree are astringent and have been used in leather tanning and for dying black. The timber is tough and hard wearing and has been used for all sorts of implements such as staves, poles and hoops for barrels. The berries yield a delicious jelly which is excellent with cold game or wildfowl and a wholesome kind of perry or cider can also be made from them.

The bark, leaves and fruit were all said to have herbal medicinal properties. A decoction of the bark has been given for diarrhoea and coughs and the ripe berries provide an astringent gargle for sore throats, inflamed tonsils and (somehow) as a remedy for haemorrhoids! The leaves were used as a poultice for sore eyes. The anti-scorbutic properties of the berries have also been used as a treatment for scurvy (Grieve 1931; Allen & Hatfield 2004).

Folklore

In Irish folklore (and in Scotland and Scandinavia also to some extent), the Rowan has always been considered a tree of formidable magical and protective powers against evil forces, due to its bright flame red berries. An alternative name 'Quicken' refers to its 'quickening' or life-giving powers, while the Irish Gaelic name 'Caorthann' derives from the word 'caor', which means both a berry and a blazing flame (Mac Coitir 2003). A Rowan was planted near cottages or a branch was hung inside to prevent fire-charming (ie avoiding danger from fire) and used to keep the dead from rising. It was also tied on a hound's collar to increase its speed in the hunt.

A Rowan walking stick offered good protection from the fairies, as did a cross made of the wood or a sprig of the plant on the hat. Above all, it was used to protect milk and its products from supernatural harm, was kept in the byre to protect the cows, and put in the pail and around the churn to ensure that the 'profit' in the milk was not stolen. Branches were put over the door lintels of houses, barns, stables and any other farm buildings to ward off witchcraft. In Scotland, flail rods were made of Mountain Ash to keep witches from threshing the corn and stealing the grain. Rowan magic appears in numerous Irish legends and myths also, including The pursuit of Diarmaid and Gráinne (Vickery 1995; Mac Coitir 2003).

Threats

None.