Sorbus aucuparia (Rowan or Mountain ash)

S. aucuparia is strongly connected to folklore, its tough but flexible wood has been used in construction and furniture making, its fruit in culinary creations, beverages, as a medicinal remedy and fodder for livestock. S. aucuparia is known by many other names for example, in old English as ‘cwic-beám’ or ‘quick beam’, in Irish ‘caorann’ due to the beauty of its berries. In Canada it is referred to as the ‘dogberry’ tree, the ‘Vogelbeerbaum’ (bird-berry tree) or Eberesche in German. The Welsh name is ‘criafol’ or ‘lamenting fruit’ (the red berries), which according to tradition are associated with the blood of Christ and that the cross was carved from the wood of this tree. But S. aucuparia is more commonly know as the ‘Rowan’ and/or ‘Amur mountain ash’ as it grows well at high altitudes. It is hardy can tolerate shade or full sun, drought and severe cold periods and grows in many different soil conditions, dry to damp, acidic, clay, sandy soil and wet peat, but it does not tolerate water logging or saline soil.

S. aucuparia a monoecious species is indigenous to most of northern Europe, Iceland, Russia, northern China, north America and Canada is one of the shortest-lived trees approximately 80 years. It can grow depending on altitude and terrain from 5 to 15m in height often in multiple trunk form, averaging 40cm diameter, cylindrical and slender. Its bark is yellowish grey when young becoming greyish black when mature, which eventually cracks and descales. The leaves are compound and pinnate having 4 to 9 pairs of leaflets arranged opposite one another along the stem or petiole with a terminal leaflet at the end. S. aucuparia is often confused with the common ash Fraxinus excelsior as the leaves of both species have similarity, but S. aucuparia and F. excelsior are not related they are entirely different species.

Image.1

From May to June large clusters appear which contain about 250 yellowish – white flowers that produce a rather unpleasant Trimethylamine odour reminiscent of bad fish. The fruit is in a green berry form averaging 8 to 10mm in diameter, which ripen from August to October turning to either orange or red in color.

Sorbus flowers and berries

 

Sorbus.1

 

Natural enemies – as with all flora S. aucuparia has its share of pests and disease and although the leaves are not actually palatable to insects, they can cause damage. Such pests include the apple fruit moth Argyresthia conjugella and the mountain-ash sawfly Hoplocampa alpina, the case-bearer moth Coleophora anatipennella and leaf miners of the genus Stigmella. Another harmful pest known to attack S. aucuparia is the Asian long-horn beetle Anoplophora glabripennis mentioned in the article ‘The colourful maple’ however, to date there have been no reported sightings of its presence. The rust fungus Gymnosporangium cornutum produces leaf galls that are unsightly, but the contagious disease ‘fire-blight’, a common problem in orchards containing apple, pears can destroy the plant.

Sorbus enemies

Fire blight disease

But one should not be deterred from using this species in bonsai as it is quite an attractive plant although its frond-like leaves are large and difficult to reduce, which deny it it the true bonsai appearence. In early spring 2015 this twin trunk S. aucuparia was rescued from a patch of wasteland being prepared for development. Its height over 2 metres was reduced (red circles) to retain movement in the two trunks and to give it a more squat robust appearance. (shown below)

S. aucuparia 2016.2017

The left image shows the tree in summer 2016 (the block of wood is there to keep the two trunks apart) and the right image depicts the tree in August 2017. As you can see some of the leaf lengths (yellow arrows) are smaller, achieved by pruning the first leaf back, but leaving a 1cm petiole to encourage a new leaf to sprout. Although S. aucuparia is considered a hardy species this particular specimen has endured some harsh treatment, 70% of the root ball removed as was most of its foliage with wiring to be done in October 2017. It is recovering, but needs time to fully recover and establish itself in its new training pot. Until next time BW, N.

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