Northern Ireland's Priority Species

Centaurium littorale – seaside centaury

 

Distribution map

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Centaurium littorale (Turner ex Sm.) Gilmour
Family: Gentianaceae

A species of damp sand dune areas only known from two sites in Ireland, both on the coast of County Londonderry.

In brief

  • Inhabits damp flat sandy areas of dune systems
  • Only known from two sites in Ireland, Magilligan and Portstewart dunes
  • Conspicuous flowers presented in July and August
  • It is rare and is restricted to Northern Ireland within Ireland
  • Can be confused with the widespread common centaury (Centaurium erythraea)
  • Very sensitive to dune management.

Species description
This species is a member of the Gentian family. It has a basal rosette of narrow leaves which are characteristically weakly one to three veined and have tips resembling spoons. From these rosettes the erect stems arise singly or in twos or threes and may be anything from 2 to 20cm tall, depending upon site conditions. The vivid pink, funnel-shaped flowers are stalkless and crowded into a head.

Life cycle
Seaside centaury is a winter annual, meaning the seeds germinate in the autumn to overwinter as seedlings, most of which subsequently flower in July and August of the following year, then die back in the late summer of the same year. A proportion of the population may take two or more years to flower. The seed dispersal is poor, so plants may be found in quite dense colonies.

Similar species
There are three species of Centaury in Ireland, all superficially similar and all quite variable. Lesser centaury (Centaurium pulchellum) only occurs in the Republic of Ireland where it is rare and protected; however, common centaury (Centaurium erythraea) is widespread throughout Ireland in many habitats and can be particularly common in the dune habitats shared by seaside centaury.

It may take close examination to separate these species, especially early in the growing season when the leaves of common centaury have not fully developed. Any plant with elliptic, five-veined leaves is common (not seaside) centaury. In addition, whilst common centaury leaves are smooth, seaside centaury leaves are usually somewhat rough.

To add to the possible confusion, these species are known to hybridise, and plants that are intermediate in character are often found where the two parents co-exist; these have been extensively studied by Dr. Ubsdell. The length of the sepals compared to the tubular petals plus the shape of the tip of the stigma are used to distinguish between these species and intermediates with certainty.

How to see this species
This is a species exclusively of dunes, particularly damp dune slack sides. One of Reverend Coslett Herbert Waddell’s last contributions to Irish botany was to discover seaside centaury at Portstewart in 1913, on the dune system between the town and the River Foyle. It was then a first Irish record, and remains one of only two places in Ireland where this species has been recorded, the second being some 15km west along the coast in the huge dune fields of Magilligan Point. Portstewart dunes are probably the best place to see this plant in Ireland. It is most conspicuous when flowering in mid- to late summer.

Current status
Species of the genus Centaurium are primarily distributed in the Mediterranean basin, but seaside centaury extends from the northern Mediterranean to Scandinavia and the Baltic states and, though widespread, is not common anywhere in its range. It is only known from two sites in Northern Ireland, and not recorded from the Republic of Ireland.

All wild plants are given some measure of protection in Northern Ireland under the Wildlife (NI) Order, 1985. Seaside centaury is one of the fifty-six species, listed in Schedule 8, parts 1 and 2, which are given special protection. This means that without a licence from the Environment and Heritage Service, it is illegal to pick intentionally, uproot or destroy the plant or even collect the flowers or seeds.

Why is this species a priority in Northern Ireland?

  • Rare, confined to a small population of one or two sites in Northern Ireland with the Irish population being restricted to Northern Ireland.

Seaside centaury is classified as ‘Scarce’ in Britain by the BSBI, and as ‘Nationally Scarce’ by the JNCC.

Threats/Causes of decline
As a plant of dune systems, it is vulnerable to natural shifts in the dune structure and morphology, and to the acceleration of erosion, for example, by recreational use.

Overgrazing, trampling and dunging by livestock, especially cattle may be damaging to this species, but it is also sensitive to undergrazing; it cannot compete in vegetation that is allowed to grow tall. Rabbits are often important grazers of sand dune systems and implicated in maintaining a suitable open sward for seaside centaury, so the success of this plant may be directly linked to factors affecting the population of rabbits. In some sites where the grazing pressure has been reduced, it has been noted that this species quickly becomes confined to the sides of trampled paths.

Conservation of this species

Current action

  • The designated sites of the Bann estuary and Magilligan ASSIs/SACs, between them are thought to cover the entire Irish population of this species
  • Implementation of the Northern Ireland Habitat Action Plan for Coastal Sand Dunes.

Proposed objectives/actions

  • Maintain the number of viable populations of the species.

What you can do
If visiting either of the known sites for this species refrain from collecting or otherwise damaging specimens. If plants suspected of being this species are located elsewhere in Northern Ireland, careful notes should be made of the location and details submitted to the Botany Department of the Ulster Museum. Any records can be sent to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU, Tel: 028 9039 5256 or email cedar.info [at] magni.org.uk.

Further information

Links
http://www.bsbi.org.uk/Status2005.xls

JNCC web page listing Nationally Scarce vascular plants

Flora of Northern Ireland

Information on ASSIs

Northern Ireland Habitat Action Plans

Kew Bibliographic Databases

Literature
Ubsdell, R. (1972). The status of some intermediates between Centaurium littorale and Centaurium erythraea from the Lancashire coast. Watsonia 9(2): 204.

Ubsdell, R. (1974). A natural hybrid in Centaurium. Watsonia 10(2): 231.

Ubsdell, R.A.E. (1976). Studies on variation and evolution in Centaurium erythraea Rafn. and C. littorale (D. Turner) Gilmour in the British Isles: 1. Taxonomy and biometrical studies. Watsonia 11(1): 7-31.

Ubsdell, R.A.E. (1976). Studies on variation in Centaurium erythraea Rafn. and C. littorale (D. Turner) Gilmour in the British Isles: 2. Cytology. Watsonia 11(1): 33-43.

Ubsdell, R.A.E. (1979). Studies on variation and evolution in Centaurium erythraea Rafn. and C. littorale (D. Turner) Gilmour in the British Isles 3. Breeding systems, floral biology and general discussion. Watsonia 12(3): 225–232.

Text written by:
Shaun Wolfe-Murphy