Northern Ireland's Priority Species

Coeloglossum viride – frog orchid

 

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.

 

Coeloglossum viride (L.) Hartman
Family: Orchidaceae

Frog orchid is inconspicuous and very easily overlooked. It is a small, brownish-green erect plant, usually 10-20 cm in height but quite often smaller. Its size and colours allow it to blend into the surrounding vegetation and effective hide it. Fortunately for the field botanist it very often accompanies a number of much more obvious orchid species, including Fragrant orchid (Gymnadenia conopsea) and Common spotted-orchid (Dactylorhiza fuchsii). C. viride grows on infertile, base- or lime-rich soils, that vary from dry to rather wet, support grazed grasslands, and range upwards from coastal lowlands (including dune systems), to mountain ledges and flushes.

In brief

  • Flowers from May to August, very occasionally to September
  • Local to abundant in suitable well-grazed habitats, but populations vary considerably from year to year
  • Restricted to base- or lime-rich soils
  • Upland sites tend to involve some degree of soil mineral enrichment (i.e., flushing by mineral-containing ground water)
  • Decidedly local in Northern Ireland, definitely declining in some counties while surviving rather well in others
  • Beyond our shores it is a widespread Circumpolar Boreal-montane species

Species description
A small tuberous perennial herb, typically with reddish- or brownish-green leaves, bracts and flowers, although occasionally greener than this might suggest. The plant bears 2-6 strap-shaped or oblong, dark green leaves concentrated towards the stem base, above which develops the cylindrical, lax spike of 5-20 flowers. The lowermost leaves are 3-10 cm long, oblong and spreading. The flowers are greenish, tinged with brown or red. The sepals form a loose hood which covers and hides the petals. The lower lip of the flower (the labellum) is 4-8 mm long and strap shaped; its apex is minutely three-lobed. The spur is very short, 2 mm, greenish-white, almost globular in appearance.

Life cycle
The flower is slightly scented and attracts small insects which act as pollinators. The microscopically minute seed is wind dispersed and germinates in spring. Growth is enabled by a mycorrhizal fungal association and it appears to be quite rapid. The first green leaves appear within one to three years after germination, and flowering generally takes place the same year (Harrap & Harrap 2005). C. viride is uncompetitive and therefore requires grazing to minimise negative interactions from associated plant species to allow it to persist in grassland. Individual plants are short-lived, many of them fruiting only once.

Similar species
None when in flower, or in its characteristic habitat.

How to see this species
Frog orchid is very characteristic of the margins of marshy ground, fens, and also of dry to wet limestone grassland, dune slacks and machair grasslands (coastal grasslands affected by blown sand), especially when these habitats are subject to light to moderate levels of grazing pressure. It can also occur in a wider range of calcareous grasslands including upland flushes, limestone pavement, screes, rock ledges, roadsides and in old quarries. In Northern Ireland it is readily found in suitable coastal sites (e.g. Whitepark Bay, Co. Antrim), but it is also frequent and widely recorded inland in Co. Fermanagh. Frog orchid is very frequent also in the Burren, Co. Clare. As it is often very small, crouching for a low-level scan in suitable habitat can prove advantageous for finding it!

Current status
In Britain colony decline of this orchid began prior to 1930, and there has been a loss of over 50% of all recorded sites since 1987. There has also been some loss of habitat in Ireland, but not on such a large or dramatic scale. However, in Northern Ireland better recording has produced a considerable number of new sites in recent years, particularly in counties Fermanagh and Antrim, making these areas somewhat of a stronghold for this orchid.

Why is this species a priority in Northern Ireland?
Frog orchid is listed as a Priority species of Conservation concern in Northern Ireland on account of its being listed as UK Priority Species (Species of Principal Importance in England and Wales), which has suffered a major decline. Another reason is that parts of Northern Ireland currently represent strongholds of this species.

Threats/Causes of decline
In the past, Frog Orchid was associated with damp, infertile, permanent limestone pastures where the hopping amphibian itself was frequent. Nowadays, apart from marginal or inaccessible ground, these grasslands have virtually all been destroyed by agricultural 'improvements' during the last half century. C. viride declines are mainly due to the ploughing of old permanent pastures, drainage and other improvements of soil fertility. The orchid is particularly sensitive to the application of fertiliser.

Conservation of this species

Current action

  • The plant is listed as a Northern Ireland Priority Species of Conservation concern and a Biodiversity Action Plan will be prepared
  • Many of the known sites are monitored on an ad hoc basis by field botanists

Proposed objectives/actions
he status of Frog orchid will be surveyed and monitored and appropriate conservation action undertaken if required.
Recent molecular studies have shown that this species really fits within the clade of the genus Dactylorhiza, and it should become reclassified as D. viridis (L.) R.M. Bateman, A.M. Pridgeon & M.W. Chase (Bateman et al. 1997).

What you can do
You can assist by helping to monitor the health and size of populations. Any sites additional to those currently known would be of great interest. All records should be reported to either the Botanical Society of the British Isles (BSBI) or to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, Co. Down, BT18 0EU. Tel: 028 9039 5256, email: cedar.info@magni.org.uk.

Further information

Links
BSBI distribution map for Frog Orchid

Online Atlas of the British & Irish FloraFlora of Northern Ireland

Images of Frog Orchid on Irish Wildflowers site

Literature
Bateman, R.M., Pridgeon, A.M. and Chase, M.W. (1997). Phylogenetics of subtribe Orchidinae (Orchidoideae, Orchidaceae) based on nuclear ITS sequences. 2. Infrageneric relationships and reclassification to achieve moniphyly of Orchis sensu stricto. Lindleyana 12: 113-141.
Curtis, T. & Thompson, R. (2009). The Orchids of Ireland. National Museums Northern Ireland.
Foley, M. & Clarke, S. (2005). Orchids of the British Isles. Griffin Press in association with the Royal Botanic Garden, Edinburgh.
Harrap, A. & Harrap S. (2005). Orchids of Britain and Ireland. A & C Black, London.
The Vascular Plant Red Data List for Great Britain

http://jncc.defra.gov.uk/pdf/pub05_speciesstatusvpredlist3_web.pdf

Text written by:
Dr Ralph Forbes