Autumn Lady’s-tresses Orchid

Autumn Lady’s-tresses Orchid, Spiranthes spiralis, camouflaged in short grassland. © Karen Netto (Andrews)

Latin Name

Spiranthes spiralis

Genus: Spiranthes comes from the Greek words speira meaning coil + anthos meaning flower

Epithet: spiralis refers to the way the flowers spiral the stem

Vernacular Name

Autumn Lady’s-tresses highlights how the flowers resemble a braid of hair twisting around the stem.

Other Local Common Names

CountyCommon Name
DevonLady’s Tresses
HampshireLady’s Traces
YorkshireLady’s Traces
Table 1: Alternative Common Names of Spiranthes spiralis by County

Plant Family

Orchidaceae or Orchid Family

Quick ID Characteristics

Public Domain: Prof. Dr. Otto Wilhelm Thomé Flora von Deutschland, Österreich und der Schweiz 1885, Gera, Germany
Public Domain (1885): Prof. Dr. Otto Wilhelm Thomé Flora von Deutschland, Österreich und der Schweiz 1885, Gera, Germany
  • Small, tubular, trumpet-shaped, crystalline white flowers arranged in a spiral up the stem.
  • Inflorescences of 5-15 cms in height are easily missed amid the grass unless you kneel down.
  • Spike bears 3-21 flowers blooming up the stem in turn.
  • Stem is greyish-green and covered with fine, white hairs and glandular hairs.
  • Sweet scent variously described as resembling honey, almonds, coconut or vanilla.
  • Basal leaves are not visible during flowering. They appear adjacent to the stem in a rosette.
  • Stem leaves resemble scales clinging to the stem.
  • Flowers from August to September and sometimes into early October.

Habitats

  • Short, dry, unimproved, nutrient-poor, open grassland
  • On calcareous soils on chalk, limestone, grassy sand dunes, shingle banks or grykes of limestone pavements
  • Less frequently found in slightly acidic heathland
  • Often discovered on clifftops in coastal locations
  • Ancient earthworks, undisturbed pastures and downs, churchyards and cemeteries
  • Abandoned arable land, old garden lawns, grass tennis courts, road verges, reservoir and river embankments
  • Likes sunny, high light locations. Dislikes shade, but will tolerate wet soils and woodland edges
  • Requires reduced competition from tall, vigorous vegetation.
  • Mowing or grazing animals (rabbits, sheep, goats) help produce ideal conditions
  • Lowland species in Britain, not usually recorded above 180 m altitude.

Climate

Average temperature January to July: 4.4 to 15.9ºC

Annual rainfall 884 mm

Basal leaf rosettes are able to withstand frost.

A mild winter followed by a wet spring and early summer offer the best conditions for flowering in the autumn. This species is known for not flowering every year.

While the species is able to withstand drought, it was noted that the hot summer of 1976 had an adverse effect on flowering with only 1.3% of plants flowering that year.

UK and Global Distribution

Link to Biological Records Centre (BRC) Atlas Distribution Map – native with mainly south, westerly and coastal distribution in England and Wales. Extends as far north as Lancashire, North Yorkshire and Isle of Man. Found on 4 Channel Islands, all the Scilly Isles, Isle of Wight and Isle of Bardsey (North Wales). Absent from Scotland. Present on the east and west coasts of Ireland: Co. Sligo, Mayo and the Burren.

Link to National Biodiversity Network (NBN) Atlas Distribution Map.

Link to Kew’s Plants of the World Online Map – Native distribution includes Albania, Algeria, Austria, Balearic Islands, Baltic states, Belgium, Bosnia-Herzegovina, Bulgaria, Corsica, Crete, Croatia, Cyprus, Czech Republic, East Aegean Islands, France, Germany, Great Britain, Greece, Hungary, Iran, Ireland, Italy, Lebanon, Morocco, Nepal, Netherlands, North Caucasus, Poland, Portugal, Romania, Sardinia, Serbia, Sicily, Slovenia, Spain, Switzerland, Syria, Transcaucasus, Tunisia, Turkey, Ukraine, West Himalaya.

Rare in Portugal. Protected status in Belgium and the Netherlands. Latter country has seen a reduction from 36 locations to just 3 and the species is expected to go extinct within 30 years. Already extinct in Denmark.

Somerset Distribution

South Somerset (VC5) Status: Not Scarce

North Somerset (VC6) Status: Not Scarce

Roe noted in his 1981 Flora of Somerset that the species was frequent on the Poldens, Mendips and other carboniferous limestone in North Somerset. He also observed that the plant is rather erratic in appearance with numbers varying considerably from year to year.

The 2000 edition of Somerset’s Notable Species Dictionary noted the species on calcareous grassland as Uncommon (U), i.e. recorded in 5-20% of tetrads in Somerset (49-195 tetrads). A tetrad is a 2 km × 2 km square on the Ordnance Survey National Grid. Tetrads are used as recording units in field botany.

The 2016 Somerset Rare Plants Group Newsletter reported that there were no recent records in 16 out of 38 hectads (42% of previous sites). A hectad is a 10 km × 10 km square on the Ordnance Survey National Grid.

Conservation Status

Great Britain Status: Near Threatened (NT)

England Status: Near Threatened (NT). Threat Criteria A2c with 27% reduction in Area of Occupancy. England has 86% of Great Britain’s coverage of the species.

A2c = Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased or may not be understood or may not be reversible, based on sub-criteria (c) – i.e. a decline in the area of occupancy of ≥ 20%.

It is sobering to note that the last English Red List reported the regional extinction (RE) of Spiranthes romanzoffiania, Irish Lady’s-tresses, for the first time in England. This species was introduced in 1957 to England. The likely cause was suggested as a range shift due to climate change. Spiranthes aestivalis, Summer Lady’s-tresses, was already recognised as extinct in both England and Great Britain as a whole.

Threats

Agricultural Intensification

Spiranthes spiralis is known to have undergone a considerable decline before 1930. This period relates to the conversion of old pastures to arable land. The decline is recognised as ongoing. Losses are attributed to agricultural intensification and undergrazing.

Undergrazing

Undergrazing leads to the dominance of coarse, competitive grasses that cast shade and crowd out these diminutive Orchids.

Urban Expansion

Former sites have been lost to urban expansion. Further sites may be lost.

Climate Change

Climate change may impact the species. Annual flowering rates are known to vary considerably according to weather conditions.

Dependence on Bumblebees

The species does not self-pollinate and is dependent on a healthy bumblebee and bee population for pollination. An Irish example demonstrates the combined threat. The Spiranthes spiralis pollinator Bombus muscorum, Large Carder Bee, has a Near Threatened status due to a decline in hay meadows and damp sand dunes.

Poor Seed Dispersal

Seeds do not disperse far from the parent plant and are slow to germinate. Existing plant communities are therefore vulnerable without active habitat conservation.

Opportunities

The beauty of Orchids attracts greater public, amateur, professional and media attention than it is possible to build in the conservation of rare, but less prepossessing species.

Increased attention to the plight of Spiranthes spiralis in Ireland led to an increase in surveys of coastal habitats. New locations were discovered and this elusive species is now considered more widespread than previously thought. Could this be replicated in Britain?

Conservation Requirements

  1. Maintenance of short grass by grazing
  2. Suspension of grazing during seed set
  3. Preservation of root fungi
  4. Ensuring agricultural fertilisers do not impact the nutrient-poor habitat
  5. Avoid trampling by people and animals
  6. Keep sites secret to discourage orchid collection
  7. Encourage persistence in coastal regions where the species appears more resilient.
A trampled Autumn Lady's-tresses Orchid
Spiranthes spiralis, Autumn Lady’s-tresses Orchid, that managed to survive damage by trampling from recent grazing cattle © Karen Netto (Andrews)

Reproduction

Pollination

Spiranthes spiralis does not self-pollinate. It has a mechanism to prevent self-pollination. It relies on bumblebees and other bees for pollination. As a late summer- and autumn-flowering species, bumblebees are the more likely pollinators as they can fly in lower temperatures than honeybees.

The column structure of the flowers is specifically adapted to the visiting pattern of its main pollinators. The spiral arrangement of the flowers and a gradual opening process from bottom to top promote cross-pollination. Research has shown that bumblebees work from the bottom up. They rarely revisit a flower, unlike other bee species and so help ensure cross-pollination.

Bumblebees are presented with the oldest open flowers first. They are free to enter open flowers, but the younger, higher flowers restrict their entry. This floral design ensures that they will touch the sticky pad (viscidium) in their hunt for nectar. A mass of pollen (pollinia) sticks to the visitor and is carried to another plant. (Claessens has a fascinating YouTube video of a Halictus bee species on Autumn Lady’s-tresses – see references at the end).

Seed Set

The seeds are very small and are dispersed by wind. They do not travel far from their parent plants to germinate. Underground development is very slow: 8 years to germinate, 11 years to first rosette of leaves, 13-14 years to first flowering.

Vegetative Spread

Spiranthes spiralis is primarily reliant on sexual reproduction. It can also spread vegetatively. A lateral bud forms on an underground stem. The new plant forms its own tubers and the connection with the parent plant dies away.

Tubers of Autumn Lady’s-tresses, Spiranthes spiralis.
Dwergenpaartje / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Root Fungi

A fungal root associate is necessary for seed germination. This orchid is mainly found in areas where the majority of rain falls in spring and autumn. Its mycorrhizal associates (root fungi) are active at these times. It is noted that rainfall is higher in British coastal regions of the south and west. Such sites must be poor in nitrogen and phosphorous. My own Somerset sightings have been on high ground well above intensively-farmed and fertilised, low-lying agricultural land and in coastal areas.

Italian researchers have found that endophytes are present in the plant’s root tissue as well. They discovered no fewer than 9 types of fungi associated with Spiranthes spiralis. Endophytes are fungi and bacteria that live inside plants without causing disease. They enhance plant growth, increase tolerance to heavy metals and improve nitrogen fixation.

Biodiversity Support

Late summer/autumn nectar supply for bumblebees and other bees.

Further Information

Plant Naming

Binomial: Spiranthes spiralis (L.) Chevall.

(L.) denotes Carl Linnaeus (1707-1778) as the first botanist to describe the species in his Species Plantarum of 1753. He gave it the name Ophrys spiralis at that time.

In 1827, the French botanist, François Fulgis Chevalier (1796-1840), moved it to the genus Spiranthes. Thus, his botanical abbreviation Chevall. also appears after the binomial. His key interests were in fungi, ferns and algae. He wrote his doctorate thesis on poisonous and medicinal hemlock.

The genus Spiranthes was set up earlier in 1817 by another French botanist, Louis Claude Richard (1754-1821). Any plant described by him will bear the abbreviation Rich. after its binomial.

Synonyms: the species bears a total of 12 synonyms which are now considered illegitimate names. However, these may sometimes be encountered in referring to older materials. According to Kew’s Plants of the World Online, these synonyms are:

  • Epipactis spiralis (L.) Crantz
  • Gyrostachys autumnalis (Balb.) Dumort.
  • Gyrostachys spiralis (L.) Kuntze
  • Ibidium spirale (L.) Salisb.
  • Neottia autumnalis (Balb.) Steud.
  • Neottia spiralis (L.) Sw.
  • Ophrys autumnalis Balb.
  • Ophyrs spiralis L.
  • Serapias spiralis (L.) Scop.
  • Spiranthes autumnalis (Balb.) Rich.
  • Spiranthes glauca Raf.
  • Tussaca autumnalis (Balb.) Desv.

Chromosomes

Chromosome number of 2n = 30 

Additional Morphological Facts

The anti-clockwise and clockwise forms appear in similar ratios. They have similar levels of pollination. Lower flowers have higher pollination rates. Research has shown that pollinators leave anti-clockwise inflorescences more quickly, but that this behaviour is not considered detrimental.

The tuberous roots are replaced annually. The old tubers shrivel and die when its resources are exhausted.

Phenology

  • The inflorescences appear above ground at the end of summer between August and September.
  • The flowers can appear days or weeks before the rosettes of leaves.
  • The leaves are visible during seed production between October and November.
  • Leaf rosettes last until late spring (May).
  • Flowering is costly for the orchid. Repeated flowering usually requires a longer recovery period than a single year under ground. There is therefore a noted variation in flowering from year to year.

Ecology

Spiranthes spiralis is mainly found in the following plant communities:

Calcareous Grassland
  • CG2Festuca ovina – Helictochloa pratensis (Syn. Avenula pratensis/Helictotrichon pratensis). Intensely grazed Sheep’s Fescue and Meadow Oat Grass by sheep and/or rabbits.
  • CG10Festuca ovina – Agrostis capillaris – Thymus drucei (Syn. Thymus polytrichus). Grassland community of Sheep’s Fescue, Common Bent and Wild Thyme in sub-community of Cirsium acaule (Dwarf Thistle) and Asperula cynanchica (Squincywort).
Mesotrophic Grassland
  • MG5Cynosurus cristatus – Centaurea nigra. Crested Dog’s-tail and Common Knapweed in sub-community of Galium verum (Ladies’ Bedstraw).

Plant Diseases

A rust, Uredo oncidii, can infect the leaves and stems.

History

The species was first mentioned in Britain in 1548 by the British natural historian, William Turner (1509-1568). He has been described as the father of English botany.

Cultural References

Postage Stamps

Spiranthes spiralis featured in a set of 2 stamps for a denomination of 2.00 BAM for Bosnia and Herzegovina. It was produced by Croatian Post Ltd and released on 1 November 2018. The other stamp bore a picture of Daphne bigayana and was also for 2.00 BAM.

© Karen Netto (Andrews)

References and Further Reading

%d bloggers like this:
search previous next tag category expand menu location phone mail time cart zoom edit close