Spiranthes romanzoffiana

Tracheophyta MagnoliopsidaOrchidaceaeSpiranthesSpiranthes romanzoffiana

Ecology

A rhizomatous herb of acidic, nutrient poor, periodically flooded or flushed vegetation, often growing on peaty soils by rivers, streams and lake margins. It frequently occurs amongst Molinia caerulea in pastures grazed by cattle or ponies. Reproduction is mostly vegetative in our area. Lowland.

Status

Native

World Distribution

Oceanic Boreal-montane element; in Europe restricted to Britain and Ireland but widespread in N. America.

Broad Habitats

Fen, marsh and swamp (not wooded)

Light (Ellenberg): 8

Moisture (Ellenberg): 8

Reaction (Ellenberg): 6

Nitrogen (Ellenberg): 4

0

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 4.4

July Mean Temperature (Celsius): 14.1

Annual Precipitation (mm): 1248

Life form information

Height (cm): 25

Perennation - primary

Perennial

Life Form - primary

Hemicryptophyte

Woodiness

Herbaceous

Clonality - primary

Little or no vegetative spread

Count of 10km squares in Great Britain: 21

Count of 10km squares in Ireland: 44

Count of 10km squares in the Channel Isles: 0

Atlas Change Index: 0.45

Distribution information

JNCC Designations

NBNSYS0000002298

Scarce Atlas Account

Scarce Atlas Account: 

Spiranthes romanzoffiana Cham.

Irish lady's-tresses

Status: scarce

 

This is a plant with a distinctive habitat, this being the Molinia caerulea carpet on old lazy beds grazed by cattle. Some sites are subject to inundation in winter. However, three of the five largest known populations in Britain are not inundated, but have trickles flowing through them from occasional flushes. Ideally, sites should be grazed by cattle when the plant is dormant. In 1972, John Raven noted that the species was unusually abundant in an area where cattle had been fed throughout the preceding winter. It is confined to the lowlands. 

There is no direct evidence of cross-pollination in Britain, and our populations are believed to reproduce entirely vegetatively. A lateral bud (very rarely two) develops at the base of the stem during the growing season. This bud overwinters, and produces the following year's aerial parts. Disturbance seems to stimulate dormant plants. One of our largest populations has produced approximately one hundred flowering spikes consistently for at least the last five years (J.H. Robarts pers. comm.).

Though formerly included in the Red Data Book (Perring & Farrell 1983) more sites have been found recently because the species has been deliberately searched for in likely places. It may have been under-recorded in the past as it is very difficult to see when not in flower because of its grass-like leaves.

S. romanzoffiana is a member of the small North American element in our flora. It is confined to Britain and Ireland in Europe, but it is widespread in North America, including the Aleutian Islands.

 

F. Horsman

PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.

Atlas text references

Atlas (334b)
Allan B, Woods P
1993.  Wild orchids of Scotland.
Curtis TGF, McGough HN
1988.  The Irish Red Data Book. 1. Vascular Plants.
Gulliver RL
1996.  The status of Spiranthes romanzoffiana Cham. (Orchidaceae), Irish Lady's Tresses, on Colonsay (v.c. 102) in 1995; with special reference to associated plant communities. Watsonia. 21:202-204.
Hultén E, Fries M
1986.  Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Pearman DA, Preston CD
2000.  A Flora of Tiree, Gunna and Coll.
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.