Northern Ireland's Priority Species

Teesdalia nudicaulis – shepherd's cress

 

Distribution map

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Teesdalia nudicaulis (L.) R.Br.
Family: Brassicaceae

A local species of sand dunes in Dundrum Bay, County Down and the County Londonderry coast at the Bann estuary and Benone. Also formerly known from a sandy shore on Lough Neagh in County Tyrone. Only native in Ireland at these sites.

In brief

  • Now restricted to sand dunes in Dundrum Bay, County Down and on the County Londonderry coast
  • Best seen in April-June when it is flowering
  • Northern Ireland holds the entire Irish population of this species
  • Threatened by scrub invasion.

Species description
A delicate little annual crucifer with an overwintering rosette of lobed leaves from which arise flowering stems reaching about 15cm maximum. Flowers very small and white. Fruit flattened-oval with a notch.

Life cycle
The flowers are probably self-pollinated. The fruits contain four seeds. Germination of the seed takes place soon after release from the fruit and results in the formation of a leaf rosette and long taproot. The plant passes the winter in this form — with the rosette pressed closely to the sand surface. Flowering shoots are produced in the following spring. Death of the plant follows shedding of the seed.

Similar species
Other small white-flowered crucifers such as bittercress (Cardamine hirsuta), or small plants of shepherd’s purse (Capsella bursa-pastoris) could be mistaken perhaps for shepherd’s cress, but close attention to the shape of the fruit and other details such as leaf-shape will easily distinguish these plants.

How to see this species
The plant is best looked for on bare sand in Murlough Dunes National Nature Reserve, Dundrum, County Down. Its appearance at the other sites is less predictable. It is best seen from April to June when it is flowering.

Current status
There are three dune sites where this species has been seen in the past thirty years: Murlough, County Down, Grangemore by the Bann Estuary, County Londonderry and Benone, County Londonderry. Of these the plants at Murlough appear to be the most predictable in their appearance, and it is possible that it has been lost from Benone since its last recorded appearance in 1971. Also reported from Ballykinler dunes but not seen there since 1914.

Shepherd’s cress also once grew on a sandy lake shore at Washing Bay, Lough Neagh in County Tyrone (its first reported site in Ireland), but is almost certainly extinct there. Sand excavated from this site was the source of a number of records of this plant as a casual at other inland sites: it has not persisted at these sites. It is protected under the Wildlife Order (NI) 1985.

Why is this species a priority in Northern Ireland?

  • It is rare and Northern Ireland holds all the native Irish population of shepherd’s cress.

It is listed as rare in the Irish Red Data Book.

Threats/Causes of decline
The loss of the Washing Bay population at some time after 1944 may have been associated with sand extraction from the site and also a reported conversion of its habitat to playing fields.

Elsewhere, the loss of its open sandy habitat by encroachment of scrub may be one factor in its decline in Co. Londonderry: also the development of a caravan park at Benone. Scrub encroachment and habitat destruction by development remain the principal threats to its survival.

Shepherd’s cress has a very short-lived seed bank which will prevent recovery of lost or populations or damaged sites.

Conservation of this species

Current action

  • Murlough Dunes is a National Nature Reserve
  • Grangemore is within the Bann Estuary ASSI
  • Grangemore is also within the Bann Estuary Special Area of Conservation
  • Implementation of the Northern Ireland habitat action plan for Coastal Sand Dunes.

Proposed objectives/actions

  • Maintain the number of viable populations of this species
  • Maintain the range of this species
  • Establish appropriate management on its known sites
  • If refound at ‘lost’ sites, ensure that the population is maintained.

What you can do
Reports of this species are always useful, especially from any County Londonderry sites. 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 Tel: 028 9039 5256, cedar.info [at] magni.org.uk.

Further information

Links
Flora of Northern Ireland

Bann Estuary ASSI.

Murlough National Nature Reserve

Northern Ireland Habitat Action Plan for Coastal Sand Dunes

Literature
Curtis, T.G.F. and McGough, H.N. (1988). The Irish Red Data Book – 1 Vascular Plants. Stationery Office, Dublin.

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.

Salisbury, E. (1952). Downs and Dunes. G. Bell & Sons Ltd., London. (Pages 241-4).

Text written by:
Paul Hackney