Northern Ireland's Priority Species

Sagina subulata – heath pearlwort

 

Distribution map

Click here to view an interactive map of the Northern Ireland dataset as currently collated by CEDaR.
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Sagina subulata (Sw.) C.Presl
Family: Caryophyllaceae

A perennial, mat-forming species which in Ireland is confined to rocky open coastal heathy grassland where it appears to have undergone a recent decline. As it is a diminutive plant, it may have been overlooked, but there is cause for concern for this plant.

In brief

  • In Northern Ireland it is restricted to a few bare rocky areas of heathy sea cliffs
  • Formerly recorded from several such sites, mainly along the north coast, but now its range is severely contracted. The only recent records are from the sea cliffs around Ballycastle
  • A diminutive plant that is inconspicuous for much of the year, but with striking white flowers in the summer
  • It appears to have undergone a rapid decline
  • The causes of this decline are currently unknown.

Species description
It is a member of the campion family, which apart from the showy carnations, pinks and campions, includes a number of smaller, weedier species. The most common members of the genus Sagina in Northern Ireland are annual species which form mossy clumps with inconspicuous flowers, often with petals described as ‘wanting’, such as procumbent pearlwort (Sagina procumbens), which may be commonly found on pavements and, to gardeners dismay, in lawns. The rosettes of heath pearlwort also form low cushions, but with attractive pure white starry flowers borne on hair-like flower stalks arising from around the margins. By comparison gardeners are happy to plant this species between pavers, where it may be called ‘Irish moss’. The official English name for Sagina subulata is heath pearlwort; another alternative name, awl-leaved pearlwort, is more descriptive as the short linear leaves have a bristle-like point at the tip. These occur in opposite pairs throughout, and although they look needle-like, they are not stiff and are more sticky than sharp to the touch, due to glandular hairs. Be aware that much Irish material has glabrous flower stalks and fails to ‘key out’ in many identification guides.

Life cycle
This is a perennial species. Flowers are presented from June to August — long enough to attract insects to cross-pollinate plants, but despite its showy flowers, little nectar is produced and they receive few insect visitors. Instead, flowers automatically self-pollinate. Seeds may persist for years in the soil.

Similar species
The only other pearlwort in Northern Ireland with showy flowers is knotted pearlwort (Sagina nodosa) which grows in very different habitats (calcium-rich marshes), and has larger petals which are almost twice the length of the sepals. Even when not in flower, the challenge is to find, rather than to identify, this species — its sticky foliage and leaves with needle tips, which are almost as long as the leaf is wide, are quite characteristic.

How to see this species
In strongholds for this species, such as western Scotland and the south-west peninsula of England, it can grow in inland situations. In Northern Ireland, it is restricted to a few bare rocky areas of heathy sea cliffs. The only recent records are from the sea cliffs around Ballycastle. It is an easy plant to overlook when not in flower, so is best searched for between June and August when it bears its conspicuous white flowers. Relevant access permissions should always be sought prior to visiting any sites.

Current status
This is a coastal species in Ireland. It has been recorded very sparingly from most of the counties of the western seaboard but otherwise, only from the coasts of counties Londonderry and Antrim, especially around Fairhead, Ballycastle and Rathlin, but as far south as Islandmagee. Since 1987 it has only been recorded from around Ballycastle and from a new location in the Lecale, County Down.

Why is this species a priority in Northern Ireland?

  • Rapid decline (2 per cent per year).

The BSBI Atlas2000 project highlighted the apparent disappearance of this species from many of its former sites along the north coast; this includes often-visited sites such as the Giant’s Causeway.

Threats/Causes of decline
The reason for the apparent decline must be a matter for speculation; certainly the plant would be sensitive to habitat loss, or to changes in the management of coastal grassland, such as fertilisation and grazing intensity.

Conservation of this species

Current action

  • Several areas of cliffs and semi-natural grassland along the Antrim coast are included in ASSIs, such as Carrickarade and White Park Bay.

Proposed objectives/actions

  • Maintain the number of viable populations of the species
  • Increase the number of viable populations of the species
  • If refound, ensure that the population is maintained.

What you can do
Keep an eye out for this plant in rocky coastal grassland anywhere in Northern Ireland in the summer. Check any mossy vegetation with white flowers, and if it appears to be this species, report its exact locality 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
Flora of Northern IrelandInformation on ASSIs

Literature

Text written by:
Shaun Wolfe-Murphy