Sorbus × hybrida

Sorbus × hybrida
Foliage and fruit
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Rosales
Family:	Rosaceae
Genus:	Sorbus
Subgenus:	Sorbus
Species:	S. hybrida
Binomial name
Sorbus hybrida L.
Synonyms[1]
Sorbus fennica (Kalm) Fr.

Sorbus hybrida, the oakleaf mountain ash,^[2] Swedish service-tree^[3] or Finnish whitebeam, is a species of whitebeam native to Scandinavia in Norway, eastern Sweden, and southwestern Finland, and locally in the Baltic States in Latvia.^[4][5][6]

Leaf; under side (left) and upper side (right)

It is a medium-sized deciduous tree growing to 10–15 m tall with a stout trunk up to 60 cm diameter and grey bark; the crown is columnar or conic in young trees, becoming rounded with age, with branches angled upwards. The leaves are green above, and densely hairy with white hairs beneath, 7–12 cm long and 5–8 cm broad, lobed, with six to nine oval lobes on each side of the leaf, broadest near the base with the two basal pairs of lobes cut right to the midrib as separate leaflets, rounded at the apex, and finely serrated margins. The autumn colour is dull rusty brown. The flowers are 20 mm diameter, with five white petals and 20 yellowish-white stamens; they are produced in corymbs 6–11 cm diameter in late spring. The fruit is a globose pome 12–15 mm diameter, bright red, maturing in mid autumn. The fruit is succulent, and eaten by thrushes and waxwings, which disperse the seeds.^[4][6]

It is a tetraploid species of hybrid origin between S. aucuparia (European rowan) and S. intermedia (Swedish whitebeam),^[5] the latter being a tetraploid triple hybrid between S. aucuparia, S. torminalis, and either S. aria or one of its close relatives.^[7][8] S. intermedia differs from S. hybrida in having the leaves less deeply lobed with no separate leaflets. Closely related Sorbus meinichii is a triploid or tetraploid species of hybrid origin between S. hybrida and S. aucuparia^[9][10] and differs in having the basal four to six pairs of lobes cut right to the midrib as separate leaflets. All three polyploid species are apomictic species which breed true without pollination.^[4]

Cultivation and uses

Sorbus × hybrida is grown as an ornamental tree in northern Europe, and is locally naturalised in the British Isles.^[4] The cultivar 'Gibbsii' has gained the Royal Horticultural Society's Award of Garden Merit.^[11]

References

1. "The Plant List".
2. "Sorbus hybrida". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 24 November 2015.
3. "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-02-25. Retrieved 2014-10-17.
4. Rushforth, K. (1999). Trees of Britain and Europe. Collins ISBN 0-00-220013-9.
5. Den Virtuella Floran: Sorbus hybrida (in Swedish; with maps)
6. Vedel, H., & Lange, J. (1960). Trees and Bushes in Wood and Hedgerow. Metheun & Co. Ltd., London.
7. Nelson-Jones, E.B.; Briggs, D.; Smith, A.G. (2002). "The origin of intermediate species of the genus Sorbus". Theoretical and Applied Genetics. 105 (6–7): 953–963. doi:10.1007/s00122-002-0957-6.
8. Chester, M.; Cowan, R.S.; Fay, M.F.; Rich, T.C.G. (2007). "Parentage of endemic Sorbus L. (Rosaceae) species in the British Isles: evidence from plastid DNA". Botanical Journal of the Linnean Society. 154 (3): 291–304. doi:10.1111/j.1095-8339.2007.00669.
9. Bolstad, A. & Salvesen, P. (1999). "Biosystematic studies of Sorbus meinichii (Rosaceae) at Moster, S. Norway". Nordic Journal of Botany. 19: 547–559. doi:10.1111/j.1756-1051.1999.tb01138.x.
10. Liljefors, A. (1953). "Studies on propagation, embryology, and pollination in Sorbus". Acta Horti Bergiani. 16: 277–329.
11. "RHS Plant Selector - Sorbus × hybrida 'Gibbsii'". Retrieved 4 July 2013.