Journal Number 93
November 2005


BRITISH ORCHIDS

Early Marsh-Orchid (Dactylorhiza incarnata (L.) SoĆ²)
By David Lang

The Marsh-orchids all belong to the genus Dactylorhiza - literally "finger-rooted", on account
of the shape of the tubers. They are a complex group, prone to hybridisation with fellow members of the Marsh-orchid group and also with the Spotted-orchids, which belong to the same genus. The resulting populations can be so-called "hybrid swarms", which are difficult to determine.

The Early Marsh-orchid is widely distributed as a species throughout all parts of Britain and Ireland, except south-east and most of south-west England where it is rare. It has been much reduced in recent years by the draining of wetlands. This overall picture masks a fascinating picture, since the species exists as five well defined sub-species, each with its own habitat requirements, which in turn dictate its distribution

     
Ssp. incarnata  

Ssp. incarnata

This is the type plant for the species. The stem is 10-30cm tall, with up to seven erect, yellowish-green, pointed leaves, which are strongly keeled and have hooded tips. The upper leaves sheath the stem, and in all forms (except ssp.cruenta) they do not have spots. The bracts are long, often tinged reddish-purple, and project from the dense flower spike.

The flowers of ssp. incarnata are pale flesh pink. The lateral sepals are marked with loops and dots, and are folded back so that they stand erect above the loose hood formed by the upper sepal and two upper inner petals.

Ssp. incarnata  

The shape of the labellum is diagnostic. It is shallowly three-lobed, the side lobes folded back tightly so that the labellum appears narrow. It is marked with a prominent double loop of dark red, within which are red dots and lines. The spur is short, fat and conical - a feature of all the Marsh-orchids and also their hybrids with the Spotted-orchids.

Ssp. incarnata grows in calcareous fens, marshes and wet meadows on base rich soils. It has in recent years successfully colonised fly-ash tips in the north of England, a discovery which was first noted by Dr.R.P.Gemmell near Salford, Manchester in 1954.

It flowers in June and early July, and is pollinated mainly by the female Red-tailed Bumble Bee (Bombus lapidarius)

     
Ssp. pulchella  

Ssp. pulchella

This is a plant of acid habitat, growing in bogs, marshes and on damp heathland. It has a wide distribution in Britain and Ireland, being the dominant form in places such as the New Forest in Hampshire, south of Dartmoor in Devon, in Anglesey and particularly in the west of Scotland. In shape and markings it is identical to ssp. incarnata, but is a distinctive mauve colour.

     
Ssp. coccinea  

Ssp. coccinea

This subspecies grows abundantly in the beautiful coastal grasslands, the machair, of north-west Scotland and the Western Isles. It also grows in huge numbers in damp dune slacks on the coast of Wales and on Anglesey, and on the coast of east Scotland in Fife. When the flowers first open they are a dazzling scarlet colour - think of the Australian Running Postman! - the squat plants having rather thick, short leaves and a dense flower spike. The sight of a dune slack carpeted in scarlet flowers is a sight to remember.

In recent years there have been inland records, once again from fly-ash tips in northern England, and also in calcareous fens. There is a closely related Continental subspecies lobelii (stat. nov.), but work by Prof H.Ae. Pedersen clearly differentiates the Welsh form from that in Holland and Denmark.

     
Ssp. cruenta  

Ssp. cruenta

This subspecies is clearly separated from the other four by the markings on the leaves, which are heavily spotted on both surfaces in the distal third. The bracts are often heavily tinged with purple and bear purple spots.

It grows in alkaline or neutral soil, and is well known in the limestone area of the Burren in Co. Clare, Ireland, where it can be found particularly on the margin of the seasonal lakes - the turloughs. It is also found in the west of Ireland in Mayo.

Then in 1982 it was discovered for the first time outside Ireland near Ullapool, West Ross in the north-west of Scotland. Two sites are now known, and the subspecies could well be overlooked elsewhere.

     
Ssp. ochroleuca  

Ssp. ochroleuca
 

This subspecies was first found in Britain by Ted Lousley in an alkaline fen in Norfolk in 1936, where Pugsley later found a second colony nearby. It is a rather tall plant, characterised by straw-coloured flowers which lack the normal loops and spots on the labellum. It flowers some two weeks later than ssp. incarnata. It had been recorded prior to 1977 from a number of localities in Norfolk, Suffolk, Cambridgeshire and Hampshire, but has declined dramatically over the last fifty years until only two populations remain and it appears to be on the verge of extinction in Britain. It is highly sensitive to a drop in water level, and widespread drainage has probably hastened its demise.

Albino ssp. incarnata are easily confused with this subspecies, and may even have a yellowish flush at the base of the labellum.

 

The Marsh-orchids and the Spotted-orchids are often treated by orchidophiles as the poor relations of the orchid flora of Britain, but they have a charm all their own and a capability to grow in such abundance that they can dazzle the eye.

The discovery recently of Dactylorhiza incarnata ssp. cruenta in Scotland, and then D. lapponica new to Britain, also in north-west Scotland, illustrates delightfully that the era of botanical discovery is far from over. Seek and ye shall (maybe) find!

 

Bibliography

Allan B, Woods P. (1993) Wild orchids of Scotland. HMSO, Edinburgh.
Bateman RM. (1981) Dactylorhiza incarnata - Early Marsh-orchid. J.Orch.Soc. Great Britain 30: 3-5.
Foley MJY. (2000) Dactylorhiza incarnata (L.) Soo subsp. ochroleuca (Wustnei ex Boll) PF Hunt & Summerh. (Orchidaceae): A comparison of British and European plants Watsonia 23: 299-303.
Kenneth AG, Tennant DJ. (1984) Dactylorhiza incarnata (L.) Soo subsp. cruenta (OF Mueller) PD Sell in Scotland. Watsonial5: 11-14.
Lang DC. (1989) A guide to the wild orchids of Britain and Ireland. Oxford University Press.
Pedersen HAe. (2001) Late-flowering populations of Dactylorhiza incarnata (Orchidaceae): A comparison of British and European plants. Nord. J. Bot. 21(2):177-186.
Summerhayes,V.S. (1951) Wild orchids of Britain. Collins.

 

 

 

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