Irish Lady's Tresses (Spiranthes romanzoffiana Cham.)

 

Irish Lady's Tresses   (Spiranthes romanzoffiana Cham.) aka Hooded Lady's Tresses in North America

Among my favourites because of its remote British locations and intriguing distribution.

Etymology

Spir- = twisted, anthos =flower

romanzoffiana = named after Nikolay Rumyanetsev (1754–1826), who was Russia's Foreign Minister and Imperial Chancellor and a notable patron of Russian voyages of exploration in the Pacific.

First Recognised in Britain and Ireland

1810 (but not reported until 1828) by James Drummond, the curator of the Cork Institution Garden, on a botanical collecting trip to what was then a remote location by land, at Castletown Bearhaven, County Cork. (Pearman)

The Plant

      

      Loch Shiel, Acharacle 13.8.18 (IMG 1384)                           Ardnamurchan 13.8.18 (IMG 1433)

      

       Loch Shiel, Acharacle 13.8.06 (IMG 2247)        Loch Shiel, Acharacle 13.8.18 (IMG 1355-7S)

        

             Ardnamurchan 13.8.18 (IMG 1411)

Description

Stems to 30cm, arising from a lateral bud on previous year's stem.   Flowers in 3 close spirals.  (Summerhayes, Stace)


Leaves

5-6, basal and on stem, erect and narrow (Summerhayes, Stace); difficult to pick out from surrounding vegetation.

      

                   Loch Shiel, Acharacle 13.8.18 (IMG 1387,8)

Leaf Edge

Entire without any teeth.

                                     

 Lower Leaf Edge x 100 (IMG 3677-86S) Field of view 1mm

Roots

Fleshy but relatively slender tuberous roots, growing down vertically especially in drier habitats (Summerhayes)

Seeds

No details

Seed Pods

No details


Habitat

Wet peaty, boggy places, often grazed by cattle and often flooded in winter.  Associated with sedges and rushes, but grows in drier places in N. America where it is more weed-like.

Mychorrhiza

No data.

Pollination

Pollinators are bees particularly Bombus pascuorum, but also B. hortorum and Apis mellifera (Claessens and Kleynen).    The fruit set percentage is probably very low.

Flowering time

Analysing the BSBI records post 2000, but excluding the Channel Isles, and any records where the date is not given in full gives 566 records for Britain and Ireland.   I think it can be assumed  that the vast majority of records are made when plants are in flower.   Looking at the median date for these records split into all Ireland, Wales and Scotland south of Glasgow (simply a reference point as the plant grows nowhere near), and Scotland north of Glasgow, gives the following flowering dates across the country:

Ireland, 323 records, median date 1 August
Wales and Scotland south of Glasgow, 11 records, median date 5 August

Scotland north of Glasgow, 218 records, median date 18 August

Flowering dates in Ireland appear to be over 2 weeks earlier than in the west of Scotland and the Hebrides.

I saw it in flower in Nova Scotia on 1 September:

Hooded (Irish) Lady's Tresses, Kejimkujik, Nova Scotia 1.9.08

Distribution in Britain and Ireland

BSBI records from 2000

Found in 23 vice counties, (Scotland 8, Wales 1, Ireland 15).   Most records are from Co. Leitrim  VCH29 (180) and Mid Ebudes VC103 (161).  In 2000-19 it was found in 134 monads, and is becoming more widespread (monads in 1960-79: 48, and in 1980-99: 99), though there may of course have been more recording activity in remote areas in the most recent decades.

Distribution Worldwide

For a European orchid species its worldwide distribution is unique.  It is a North American species broadly distributed across Canada from British Columbia to Nova Scotia, western and central US including Alaska, parts of New England. It is widely spread, and almost weed-like in places.   Britain and Ireland are the only localities in Europe.  There are various theories as to how it arrived on the west coast of Ireland - wind blown, feet of geese, but my own, rather romantic, theory is that its first appearance was in a port area in the late 18th century, which saw regular crossings between Ireland and North America, and was brought in as seed on the boots of sailors.

Hybrids and Recognised Varieties

None.   In North America there are several closely related Spiranthes species, and hybrids occur between them.

References

Pearman:  Discovery of the Native Flora of Britain and Ireland - Pearman D 2018
Claessens and Kleynen: Flower of the European Orchid - Claessens J and Kleynen J  2011
Summerhayes: Wild Orchids of Britain - Summerhayes VS 1951
Stace:  New Flora off the British Isles - Stace C 4th Edn, 2019

Updated 3.21