Northern Ireland's Priority Species

Erigeron acer – blue fleabane

 

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.

 

Erigeron acer L.
Family: Asteraceae

A stress-tolerant species that in Ireland finds the open vegetation on well-drained calcium-rich soils in which it can prosper, mainly in pits and quarries where populations can be quite ephemeral. In Northern Ireland it has a single long-standing population centred around the coastal complex of Murlough and Ballykinler in County Down.

In brief

  • A species very much restricted to open, infertile, well-drained soils
  • Only found as a natural population around Murlough and Ballykinler in County Down, but not seen there since 1992
  • Functions partially as an annual species, so more abundant some years than others.
  • Flowers in July and August
  • It is rare with Northern Ireland being the Irish stronghold
  • Listed as Vulnerable in the Irish Red Data Book
  • Well distributed, though still scarce in the East and Midlands of the Republic of Ireland, mainly in artificial habitats.

Species description
It is a member of the daisy family — the world’s largest family of flowering plants including the ragworts, dandelions and their allies. Within the family, the genus Erigeron is most closely allied to Asters.

The whole plant has sparse, long, white hairs. Stems are slender and erect rising 10 to 40cm from a leafy base. Whilst the basal leaves are oval and stalked — the classic leaf shape — numerous leaves along the stem are much more strap-shaped and clasp the stem without a leaf stalk. The stems branch above to present several flowers each 12 to 18mm in diameter, in a flat-topped cluster. Being in the daisy family, each flower has outer ray florets (these a more purplish colour than the English name suggests) and crowded inner disc florets which are a dull yellowish colour. The sepals form a cup-shaped structure that make the whole flower appear rather ‘thistle-like’.

Life cycle
Flowers appear in July and August. Within the disc, the outer disc florets are wholly female, whilst the inner contains both male and female flower parts; however, it is self-incompatible and relies upon insect visits for pollination. Once pollinated, flowers set seed from July to September. Populations which have been studied appear to comprise some individuals which are annuals, flowering once before dying, and some individuals which are short-lived perennials that survive the winter to flower in a successive season. Nonetheless, increase and spread of the population is governed by reproduction from seed rather than vegetative spread. Seed dispersal by wind is aided by the ‘pappus’, a silky yellowish-white parasail attached to each seed in the fashion of a &lsquo Dandelion clock&rsquo. Each flower may produce around 150 such seeds— high numbers of seeds, well equipped to travel, make the species potentially an effective colonist, but it is very much restricted to soils and habitats seldom encountered in Northern Ireland.

Similar species
Canadian fleabane (Conyza canadensis) was once included in the Erigeron genus, indeed the hybrid between it and blue fleabane has been identified in London. Canadian fleabane is similar in structure, but narrow-leaved throughout, and with considerably more numerous, and much smaller (3 to 5mm diameter), paler flowers. It is not native to Northern Ireland, but is increasingly being recorded from urban wastelands around Belfast.

How to see this species
This is a species of open, infertile and calcium-rich, well-drained skeletal soils. It may occur from time to time in calcium-rich substrates in excavations, but the most likely site to spot this plant is Murlough dunes, County Down, owned by the National Trust. If you are there in July or August when the plant is in flower, have a quick hunt around in open (unshaded) sparse vegetation.

Current status
This species does not appear in Professor Dickie’s 1864 Flora of Ulster as it was first discovered by Robert Lloyd Praeger more than twenty years later on the Murlough/Ballykinler dune system. This remains its only described natural population in Northern Ireland. In the past it has been described as frequent there, but has not been reported since 1992. In the Republic of Ireland it occurs in scattered locations across the midlands and Eastern counties in sandpits and quarries, on spoil and waste heaps. Though widespread, it is considered scarce.

All wild plants are given some measure of protection in Northern Ireland under the Wildlife (NI) Order, 1985, but blue fleabane is one of the fifty-six species listed in Schedule 8 which are given special protection. Under the Order it is illegal to pick intentionally, uproot or destroy plants of this species, or even to collect the flowers or seeds, unless it is under licence from Environment and Heritage Service.

Why is this species a priority in Northern Ireland?

  • It is rare, with Northern Ireland being the Irish stronghold
  • It is listed as Vulnerable in the Irish Red Data Book.

The apparent decline of the species at Murlough gives cause to question whether this species even remains a part of the Northern Irish flora.

Threats/Causes of decline
This species requires open and infertile sparse vegetation. Inappropriate management for this species would include fertilisation leading to the development of a more lush vegetation, or neglect leading to scrub encroachment. Although it is a species that is generally absent from sites heavily grazed by livestock, lack of grazing is thought to be one of the past factors mitigating against the species at Murlough. In its ruderal habitats it is vulnerable to infilling and redevelopment.

Conservation of this species

Current action

  • Murlough, County Down is a National Nature Reserve managed positively to preserve its ecologically valued wildlife by the National Trust. This includes the introduction of grazing by Dexter cattle
  • The site is designated an ASSI and SAC.

Proposed objectives/actions

  • Maintain a viable population of the species around Murlough and Ballykinler.

What you can do
Support the National Trust through membership. If plants resembling this species are found on a visit to Murlough, report the exact location to the National Trust Warden (Tel: 028 4375 1467). On any other site the find should be reported to the Botany Department of the Ulster Museum, or 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. Make careful notes as to the location of the plants, and briefly describe the habitat.

Further information

Links
Flora of Northern Ireland

Areas of Special Scientific Interest

Northern Ireland Habitat Action Plan - Coastal Sand Dunes

Literature
Wurzell, B. (1995). x Conyzigeron huelsenii in east London. BSBI News 68: 32-33.

Text written by:
Shaun Wolfe-Murphy