Northern Ireland's Priority Species

Sorbus rupicola – rock whitebeam

 

Distribution map

Click here to view an interactive map of the Northern Ireland dataset as currently collated by CEDaR.
The map is generated through the NBN Gateway using their Interactive Mapping Tool.

 

Sorbus rupicola (Syme) Hedlund
Family: Rosaceae

Rock Whitebeam occurs on the basalt and chalk cliffs of Antrim and Londonderry. Several other species of Whitebeam have been recorded in Northern Ireland but their status, as to whether they are native or are introduced, is uncertain.

In brief

  • Rock Whitebeam occurs only in Counties Antrim and Londonderry; there was also a colony of trees in Co. Down but only one has been seen recently and the whitebeams are being over-grown with hazels
  • The species usually occurs on fairly inaccessible basalt and chalk cliffs
  • Rock Whitebeam flowers in May and June but can be determined from the leaves well in to the autumn
  • The species very sparingly on the cliffs and the number of trees in Northern Ireland probably does not exceed 100
  • As many of the trees are rather inaccessible, local fires or rockfalls may well be the main threat. Grazing is a threat to trees which attempt to grow within reach of animals. In County Down trees of this species are being overgrown by hazels

Species description
The oblong leaves are toothed only in the upper two thirds, have a dark green upper surface, and are densely white-tomentose underneath. The fruits are generally quite large and wider than long. It is the second most widespread whitebeam in Britain and Ireland.

Life cycle
Like all whitebeams, Rock Whitebeam is a long-lived tree; fruiting is variable from year to year and fruit is dispersed by birds, mainly of the thursh family.

Similar species
Up to six species of whitebeams have been recorded from semi-natural conditions in Northern Ireland. Whitebeams are distinguished largely by the shape of their leaves and by the teeth or lobes on the margins of the leaves. The colour and shape of the fruits are also relevant.

How to see this species
The species can be seen high on the cliffs at the Umbra and Binevenagh as well as on some of the chalk cliffs in County Antrim. Binoculars are useful for picking out the distinctive pale underneaths to the leaves, especially in a wind.

Current status
Since 1987, the species has been seen in one hectad in each of the Counties Londonderry, Antrim and Down.

Why is this species a priority in Northern Ireland?
The species is rare with few individual trees, and the colony in County Down has been reduced to one tree since 1981.

Threats/Causes of decline

  • In County Down trees of this species are being overgrown by hazels, but trees of Rock Whitebeam which grow on cliffs in Antrim and Londonderry are not obviously under threat at present

Conservation of this species

Current action
At least one of the species’ sites, Binevenagh, has been declared an ASSI.

Proposed objectives/actions
Ensure that the current population is maintained, and if possible increased, through appropriate habitat management.

What you can do
If you think you have found this species, contact your local Biodiversity Officer
Or you can submit your records to CEDaR
The study of wild plants is an interesting hobby for anyone interested in the outdoors. The Botanical Society of the British Isles welcomes beginners to its field trips.

Further information

Links
Northern Ireland Vascular Plant Database

Literature
Day, G., Hackney, P. (2004). County Down Scarce, Rare and Extinct Vascular Plant Register. MAGNI Publication no. 016 Belfast.
Hackney, P. (1992). Stewart and Corry’s Flora of the North-east of Ireland (third Edition). Institute of Irish Studies, Queen’s University, Belfast.
Preston, C.D., Pearman, D.A. & Dines, T.D., (2002) New Atlas of the British and Irish Flora. Oxford University Press, Oxford.
Rich, T., Houston, L., Robertson, A. & Proctor, M. (2010). Whitebeams, Rowans and Service Trees of Britain and Ireland. BSBI Handbook No. 14, Botanical Society of the British Isles, London.
Stace, C.A., (2010). New Flora of the British Isles Third Edition. Cambridge University Press.

Text written by:
Robert Northridge