Sorbus Aucuparia

Sorbus aucuparia, commonly called rowan and mountain-ash, is a species of deciduous tree or shrub in the rose family. 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.

S. aucuparia 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 blossoms from May to June in dense corymbs of small yellowish white flowers and develops small red pomes as fruit that ripen from August to October and are eaten by many bird species. The plant is undemanding and frost hardy and colonizes disrupted and inaccessible places as a short-lived pioneer species.

Sorbus aucuparia occurs as a tree or shrub that grows up to between 5 and 15 m in height. The crown is loose and roundish or irregularly shaped but wide and the plant often grows multiple trunks. A trunk is slender and cylindrical and reaches up to 40 cm in diameter, and the branches stick out and are slanted upwards. The bark of a young S. aucuparia is yellowish gray and gleaming and becomes gray-black with lengthwise cracks in advanced age; it descales in small flakes. Lenticels in the bark are elongated and colored a bright ocher. The plant does not often grow older than 80 years and is one of the shortest-lived trees in temperate climate. Wood of S. aucuparia 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 600 to 700 kg/m³ in a dried state. The roots of S. aucuparia grow wide and deep, and the plant is capable of root sproutingand can regenerate after coppicing.

The compound leaves are pinnate with 4 to 9 pairs of leaflets on either side of a terete central vein and with a terminal leaflet. There are paired leaf-like stipules at the base of the petiole. The leaves are up to 20 cm long, 8 to 12 cm wide, and arranged in an alternate leaf pattern on a branch, distinguishing them from those of ash, Fraxinus excelsior, which are opposite and without stipules. The leaflets are elongated-lanceolate in shape, 2 to 6 cm long, and 1 to 2.5 cm wide with a sharply serrated edge, and have short stems or sit close to the central vein except for the outermost leaflet.

Leaflets are covered in gray-silvery hairs after sprouting but become mostly bare after they unfold. Their upper side is dark green and their underside is a grayish green and felted. Young leaflets smell like marzipan when brayed. The leaflets are asymmetrical at the bottom. S. aucuparia foliage grows in May and turns yellow in autumn or a dark red in dry locations