Rowan

Sorbus aucuparia

1. Identification and origin

The rowan (Sorbus aucuparia L.), also known as mountain ash, is an arboreal or shrubby species of the Rosaceae family, widely distributed throughout Europe, temperate Asia and mountainous regions of North Africa. In Portugal it occurs mainly in mountain and submontane areas of the North and Centre, preferring humid and cool environments. It is valued as a forest and ornamental species and for the conservation of biodiversity.

2. Economic importance

The rowan has ecological and landscape importance, being used in the afforestation of parks, the recovery of degraded areas and agroforestry systems. The fruits (rowan berries) are consumed by wildlife and traditionally used in jams, beverages and medicinal applications. The wood, although little used commercially, is dense and suitable for small carpentry pieces. The species is relevant for the conservation of pollinators and frugivorous birds.

3. Botanical characterisation

The rowan is a small to medium-sized tree, generally 8–15 m tall. The leaves are compound, imparipinnate, with 9–15 serrated leaflets. The flowers are white, arranged in dense corymbs and very attractive to insects. The fruits are globose pomes, red to orange, ripening at the end of summer and in autumn. The root system is deep and well branched, conferring good resistance to wind and moderate drought.

4. Soil and climate requirements

The species adapts to temperate and mountain climates, tolerating frost and high thermal ranges. It prefers cool, well-drained soils of medium to loamy texture, with a slightly acidic to neutral pH. It tolerates poor and stony soils, being frequent on slopes and watercourses. It requires good light, although it withstands partial shade. Fruit production is favoured by cool and humid summers.

5. Main pests

• Aphids (Aphis pomi, Dysaphis sorbi) — leaf curling and reduction in vigour
• Leafminer larva (Stigmella sorbi) — mines in young leaves
• Codling moth (Cydia pomonella) — occasional perforations in fruits
• Sawfly (Pristiphora spp.) — partial defoliation on young shoots
• Weevils (Anthonomus spp.) — damage to flower buds

6. Main diseases

• Fire blight (Erwinia amylovora) — necrosis, wilting and death of branches
• Cankers (Nectria cinnabarina, Neonectria ditissima) — corky lesions and decline
• Powdery mildew (Podosphaera clandestina) — white coating and reduction of photosynthesis
• Rusts (Gymnosporangium spp.) — leaf spots and deformations
• Root rots (Armillaria spp.) — progressive decline and death of the plant

7. General crop management

Management of the rowan is based on its establishment in cool and well-drained soils, avoiding waterlogging. Formation pruning should be moderate, favouring the natural structure of the canopy. Monitoring of aphids and wood diseases is important in young plantations. The species benefits from ground cover and high functional biodiversity. Fruit harvesting takes place at the end of summer and the beginning of autumn, according to the destination (ornamental, food or ecological).

Bibliographic references

• EPPO Global Database – Sorbus aucuparia
• CABI – Crop Protection Compendium – Sorbus aucuparia
• Roper, M., & Atkinson, M. D. (2020). Sorbus aucuparia (rowan) in Europe: ecology, distribution and silviculture. Forestry Commission Research Note.
• Houston Durrant, T., de Rigo, D., & Caudullo, G. (2016). Sorbus aucuparia in Europe: distribution, habitat, and ecology. In: European Atlas of Forest Tree Species. Publications Office of the EU.
• Rushforth, K. (1999). Trees of Britain and Europe. HarperCollins.