Northern Ireland's Priority Species

Sorbus hibernica – Irish whitebeam

 

Distribution map

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Sorbus hibernica E.Warb.
Family: Rosaceae

Sorbus hibernica is an endemic Irish tree species closely allied to Sorbus aria and S. rupicola. It is reputedly an apomictic (non-sexual species).

In brief

  • Very scattered in its distribution in Northern Ireland
  • Found in glens and on rocky scarps in scrubby woodland
  • Best seen from May to about September when it is in full leaf and in flower or fruit.
  • An Irish endemic species
  • Threatened by habitat damage or destruction of individual trees.

Species description
A small tree, sometimes stunted in rocky habitats, with rounded toothed leaves which have a dense covering of white silky hairs on the undersurfaces. The white flowers are produced in flat-topped clusters and these are followed by the globular red fruits.

Life cycle
Irish whitebeam is reputed to be an apomictic species, that is, it produces its seed and fruit without any sexual process of fertilisation. The resulting seedlings are therefore clones of the parent tree. The fruits of whitebeams are ‘designed’ to be eaten by birds which digest the flesh and pass out the stones which contain the seeds. In view of the scarcity of the Irish whitebeam, the whole process of seed dissemination, germination and establishment of young plants appears to be inefficient under present conditions.

Similar species
Closely allied to the common whitebeam (Sorbus aria) and not always easily distinguished from it. The principal differences are in the teeth of the leaf-margins (swept upwards in S. aria and straight and symmetrical in S. hibernica) and in the undersurfaces (more densely silky-hairy in S. hibernica). Both species have teeth on the leaves almost all the way around the leaf; in another closely-related species, Sorbus rupicola, the lower third of the leaf has no teeth; the leaf is also rather longer and narrower than either S. aria or S. hibernica.

S. hibernica is regarded as a rare native in Northern Ireland, but S. aria is probably an introduced species, always planted or derived from planted trees. S. aria is often found in planted hedges.

How to see this species
Irish whitebeam is very scarce in Northern Ireland and difficult to find, or to distinguish from common whitebeam, so it is best to seek expert advice before searching for it. However, a number of individual trees occur on rocky cliffs near Garron Tower, County Antrim.

Current status
Irish whitebeam has been reported from about eight or nine sites across Northern Ireland, but the precise number is unknown because of confusion with common whitebeam. The number of trees at any one site is very small, so that the total population within the Province is tiny. The principal area of occurrence is in the Midlands of Ireland.

It is a species unknown outside Ireland, although it seems to be closely similar to Sorbus eminens — a west of England and Monmouthshire endemic.

Why is this species a priority in Northern Ireland?

  • It is rare with the entire UK population contained within Northern Ireland.

It is an Irish endemic species.

Threats/Causes of decline
The principal threat is posed by the very small overall population, the tiny number of individual trees at any one site and the continuing failure of this species to expand its range or numbers. The loss of individual trees for whatever reason (such as woodland or scrub clearance, felling of individual trees or death by natural causes) would therefore have a major impact.

Conservation of this species

Current action

  • One of its principal areas of occurrence (Drumnasole and Garron Head) lies within the Antrim Coast Area of Outstanding Natural Beauty.

Proposed objectives/actions

  • Maintain the number of sites of this species
  • Maintain the range of this species
  • Establish appropriate management on appropriate sites
  • Carry out field research to locate unknown sites of this species.

What you can do
The Irish whitebeam is one of three related species in the Sorbus aria group. Distinguishing these is not always easy and any records of sites for any member of this species group are valuable. Send any records or observations to either BSBI, c/o Department of Botany, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU or to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU. Tel: 028 9039 5256, cedar.info [at] magni.org.uk.

Further information

Links
Flora of Northern Ireland

Antrim Coast and Glens A.O.N.B.

Literature

Literature
Hackney, P. (1992). Stewart & Corry’s Flora of the North-east of Ireland, 3rd edn. Institute of Irish Studies, Belfast.

Preston, C.D., Pearman, D.A. and Dines, T.D. (2002). New Atlas of the British & Irish Flora. Oxford University Press/DEFRA.

Webb, D.A., Parnell, J. and Doogue, D. (1996). An Irish Flora, 7th Edn. Dundalgan Press, Dundalk.

Text written by:
Paul Hackney