Northern Ireland's Priority Species

Gnaphalium sylvaticum – heath cudweed

 

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.

 

Gnaphalium sylvaticum L.
Family: Asteraceae

This somewhat woolly, native perennial dramatically declined during the twentieth century. It has become very rare, isolated and endangered throughout Ireland and in many parts of southern Britain. Since the plant has small, insignificant flowers, populations often fell and became locally extinct before the fact was noticed. The sudden, unexpected nature of the decline is rather mysterious and requires further study.

In brief

  • A member of the dandelion family (Compositae), heath cudweed possesses plumed, wind-dispersed seeds as its sole means of reproduction
  • It occurs in acid, damp or dry soils, often sandy or gravelly, in open, often only intermittently available habitats, either fully lit or in semi-shade
  • It is best looked for in July and August when in flower
  • It is now widely regarded as endangered, not only in Ireland and Britain, but also in North America.
  • Apart from a very few stations in the far south, all of the surviving Irish stations are in Northern Ireland
  • Despite the relatively wide range of possible habitats open to this species, both inland and coastal, it quickly declined from being widespread and locally abundant to distinct and increasing rarity.

Species description
A tufted, erect, grey-woolly-coated perennial with unbranched stems growing to 30cm or occasionally more, but often less in height. Basal leaves elongate, green on top, white-felted beneath. Contrasting small, dark brown flower heads either solitary or in clusters are arranged among slender leaves along much of the upper half of the stem.

Life cycle
Germination probably occurs in both autumn and spring, producing a basal leaf rosette from which a rather woody rootstock develops. Populations really require damp, bare, moderately acidic, lime-free soil and full, or nearly full, sunlight in order to germinate and colonize freshly available open ground. In July and August an erect or upright flowering stem arises bearing numerous small, flask-shaped flower heads of white or pink florets, surrounded by dark brown outer protective segments. Pollination is either by insects or selfing. When a species like heath cudweed becomes scarce, it is low reproductive capacity rather than rates of mortality that prevents effective exploitation of suitable habitats on the increasingly rare occasions when these become available under modern conditions.

Similar species
The only species that might possibly be confused with heath cudweed is the related annual, marsh cudweed, Gnaphalium uliginosum, a much smaller, more bushy, branched plant of damper, more muddy, sometimes seasonally flooded places near water. Its flower heads are held in a tight cluster, while those of G. sylvaticum are more spaced out along the upper stem.

How to see this species
The typical situations are sparse turf on grassy heaths, upland pastures and in canopy gaps or the better-lit margins of woods and scrub. It also frequents sand pits, gravel quarries, coastal dunes, and most especially, forestry tracks and woodland rides, and all stand a chance of having the plant present, although there may be as few as one or two individuals present. If discovered, photograph it, report it to the address below, but please do not collect any of it.

Current status
Records of this species show that there were plants found in thirteen 10Km squares in counties Tyrone, Londonderry, Fermanagh and Down during the post-1986 period. On account of being a very rare and rapidly declining plant species in Ireland, the conservation need has been recognised through declaration as a Protected Species in the Republic of Ireland.

Why is this species a priority in Northern Ireland?

  • The Irish population of heath cudweed has declined and is confined largely to Northern Ireland. It is restricted to a small number of locations.

Threats/Causes of decline
Changing agricultural practices, and especially the decline of arable agriculture in Ireland, the move to winter-sown crops and the use of herbicides and agrochemicals have together depleted to near zero the soil-borne seed bank of this species, forcing it towards smaller, more marginal, less regularly disturbed ground. In addition fertilizer run-off or other forms of soil nutrient enrichment, for example, nitrogen from car exhausts, encourages vigorous competitors, while herbicide drift kills off this species entirely.

Conservation of this species

Current action

  • Implementation of the Northern Ireland Habitat Action Plan for Lowland Dry Acid Grassland.

Proposed objectives/actions

  • Maintain the number of viable populations of the species.

What you can do
Records of new sites for this species and estimates of the size of populations are always valuable. Send to The Botanical Society of the British Isles, c/o Department of Botany, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU or CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU. Tel: 028 9039 5256, cedar.info [at] magni.org.uk.

Further information

Links
Northern Ireland Habitat Action Plan Lowland Dry Acid Grassland

Flora of Northern Ireland

Photographs on Biopix.com

Literature
Salisbury, E.J. (1942). The Reproductive Capacity of Plants. G. Bell & Sons, London.

Thompson, K., Bakker, J.P. and Bekker, R.M. (1997). The soil seed banks of North West Europe. Cambridge University Press, Cambridge.

Text written by:
Dr Ralph Forbes