Northern Ireland's Priority Species

Neotinea maculata – dense-flowered orchid

 

Distribution map

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Neotinea maculata (Desf.) Stearn
Family: Orchidaceae

Dense-flowered orchid (Neotinea maculata), also called the Irish orchid, is confined to Ireland within the British Isles, although it was reported from the Isle of Man in 1967 and survived there for twenty years. The Mediterranean area is very definitely its centre of distribution and the fact that it also occurs along the west of Ireland, as far north as counties Fermanagh and Donegal, is both extremely interesting and very puzzling.

In brief

  • This small-flowered, tuberous orchid is one of the most interesting plants in the flora of Ireland since elsewhere its world distribution is almost entirely Mediterranean

  • In Northern Ireland small populations of dense-flowered orchid are confined to two upland limestone sites in Fermanagh which were first discovered in 1986 and 1989

  • It does not occur anywhere in Britain, and in Ireland is confined to a disjointed series of sites or stations stretching between East Cork and Donegal

  • The main area of distribution and greatest frequency for this plant in Ireland remains the Burren limestones of County Clare and south-east Galway, where it was originally discovered in 1864

  • It grows in dry, warm, limestone grassland habitats

  • The orchid flowers briefly between the middle of May and the first week of June

  • Dense-flowered orchid is rare with the UK population restricted to Northern Ireland

  • The species is vulnerable to any change in its local environment, even slight changes such as minor nutrient enrichment or increased grazing pressure.

Species description
The flower spikes, which are produced on plants about 10cm tall, are composed of densely packed, small, greenish-cream, straw-coloured or pink-tinged flowers. Each flower is only 3 to 4mm across. The individual flowers do not open fully and appear permanently in bud. The few, grey-green, narrow, lower leaves are spotted with purple only when the flowers are pinkish. The lower lip-like petal of each tiny flower is three-lobed with the middle lobe wider, slightly longer than the other two and very slightly notched. There is a short, blunt spur at the base of the flower which may contain nectar. Despite this insect reward for visitors, the flowers are always self-pollinated while in bud.

Life cycle
Like all other orchids, dense-flowered orchid produces minute lightweight seed that can travel long distances on the slightest breeze. The Isle of Man plants will have originated in Western Ireland. A fungus partner in the soil assists the microscopic seed to germinate, and it also enables the juvenile green plant to develop slowly a swollen underground tuber containing food reserves. After perhaps five years development (or maybe very much longer depending upon local growing conditions), the plant develops its first flowering stem. Small basal leaves appear above ground in the autumn which overwinter and then produce the erect flowering stem in May. The individual tuber may flower every year thereafter, or just every so often. Generally the number of flower spikes in an orchid population fluctuates quite widely from year to year. Within three weeks of the flower spikes first appearing, the fruit capsules swell and vast quantities of microscopic seed are produced (Summerhayes, 1968).

Similar species
There is only one other Irish orchid with a similar appearance, Pseudorchis albida, small white orchid. It occurs in more acidic soils on heathy upland pastures. The lip-like petal in small white orchid is almost equally divided into three lobes, and the middle lobe is not notched as it is slightly in dense-flowered orchid. The nectar spur is also a little longer than in dense-flowered orchid, about one-third the length of the ovary at the base of the flower (Webb et al., 1996; Foley and Clarke, 2005).

How to see this species
This species occurs at only two sites in Fermanagh: Rahallen, south of Belmore Mountain overlooking Lower Lough Macnean, and on the top of Knockninny Hill. Here the orchid grows in dry, warm, limestone grassland habitats, developed over shallow, rocky soils on south-facing slopes. At Rahallen the plants are very thinly scattered on the warmer, south-facing slopes of sheep-grazed, short-turf grassland on rocky mounds composed of dolomitic limestone (that is, magnesium-rich limestone rock).

The Burren, County Clare is, however, still the Irish headquarters of this species though, and it is outstandingly abundant there, although still quite local in its occurrence. It is very much more rare and difficult to find at all its other Irish sites. The best time to see it is from the middle of May to the first week in June, but the seasonal pattern of flowering varies from year to year (Webb and Scannell, 1983; Harrap and Harrap, 2005). Relevant access permissions should always be sought prior to visiting any sites.

Current status
In Northern Ireland this species occurs at Rahallen and Knockninny Hill in Fermanagh. At Rahallen dense-flowered orchid appears each year in small, fluctuating numbers with a peak of 60 flowers in 2004. By comparison the population near the summit of Knockninny Hill has usually fewer than 20 plants most years, but achieved a peak of 100 flower spikes in 2004, which must have been a particularly good year for the orchid.

Why is this species a priority in Northern Ireland?
This species is rare with the UK population restricted to Northern Ireland. The entire UK population consists of two sites in Fermanagh. It is extremely rare with an interesting distribution and a small and fluctuating population.

Threats/Causes of decline
Major threats are the inherent risks associated with small, isolated, widely fluctuating populations of any species. However, the relatively long and complicated life cycle of orchid species and the small stature and low competitive ability of this one in particular, makes it vulnerable to any change in the local environment, either dramatic or slow-acting. Dense-flowered orchid tolerates quite heavy grazing pressure from sheep on the pasture grasslands, but it probably benefits from the consequent suppression of competing taller-growing plant species. Quarrying developments at Knockninny, and a slight risk from spreading bird-sown Cotoneaster microphyllus shrub at Rahallan are also of concern. Even slight changes such as minor nutrient enrichment or increased grazing pressure on the grassland could tip the fine balance between dense-flowered orchid and its competitors against the small orchid population.

Conservation of this species

Current action

  • Knockninny Hill, one of the sites for this species, has been designated as a ASSI on account of its species-rich, unimproved limestone grassland and the ash-hazel woodland on its slopes

  • Implementation of the Northern Ireland Habitat Action Plan for Calcareous Grassland.

Proposed objectives/actions

  • Maintain the number of viable populations of the species.

What you can do
If you think you have found this species, contact 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
Flora of Northern Ireland

Northern Ireland European Orchid Website

The Burren, Co Clare

Ask About Ireland

Northern Ireland Habitat Action Plan for Calcareous Grassland

Knockninny Hill ASSI

Literature
Foley, M. and Clarke, S. (2005). Orchids of the British Isles. Royal Botanic Garden Edinburgh. Griffin Press, Cheltenham.

Harrap, A. and Harrap, S. (2005). Orchids of Britain and Ireland: a Field and Site Guide. A and C Black, London.

Summerhayes, V.S. (1968). Wild Orchids of Britain. New Naturalist Volume 19. 2nd edition. Collins, London.

Webb, D.A., Parnell, J. and Doogue, D. (1996). An Irish Flora. 7th revised edition. Dundalgan Press, Dundalk.

Webb, D.A. and Scannell, M.J.P. (1983). Flora of Connemara and the Burren. Royal Dublin Society and Cambridge University Press, Cambridge.

Text written by:
Dr Ralph Forbes