Spiranthes spiralis, commonly known as autumn lady's-tresses,[1] is an orchid that grows in Europe and adjacent North Africa and Asia.

Autumn lady's tresses is a polycarp, perennial, herbaceous plant that remains underground during its dormancy in summer with tubers.

Below the flowers stand three to seven grayish green, acute leaves that envelop the stem, with membranous edges and three to five veins.

The flowers are very small, ± ½ cm (0.2 in), white, and spread a fragrance that is said to by reminiscent of lily of the valley, vanilla or almonds.

[3] Outer tepals are oblong-ovate, slightly tapering to a blunt tip, 6–7 mm (0.24–0.28 in) long, white with a light green vein, have a ciliate or very finely serrated edge, and on the outside with little glandular hairs.

[2] Around the end of August a rosette of leaves appears, which stays green over the winter and dies back in July at the latest.

Some species are found in Central and South America, in temperate and tropical Asia southward to Australia and New Zealand.

[2] The autumn lady's tresses is easily distinguished because the two other species have inflorescences that occur earlier during the year (May–July) from a living rosette, with lanceolate leaves rising at an angle and having cream-colored instead of greenish or greyish white flowers.

In G. repens the inflorescence emerges from the centre of a rosette of ovate leaves with a pointed tip, and has striking perpendicular connective veins.

Recent DNA-analysis showed that three Eurasian species of Spiranthes are most related to each other, with a clade consisting of S. sinensis and S. aestivalis being the sister group of S.

[5] The botanical name is derived from the ancient Greek σπεῖρα (speira) "spiral" and ἄνθος (anthos) "flower".

[6] Autumn lady's tresses occurs in Europe and small adjacent parts of North Africa and Asia.

To the North its limit is from northern England, the Netherlands, Denmark and the southern Baltic, Poland to western Ukraine.

In France, it occurs across the country, except for the regions of Champagne-Ardenne and Lorraine, and the departments of Nord, Aisne, Eure, Bas-Rhin, Val d'Oise and Seine-et-Marne.

Only when man created the habitat for this orchid by settling and converting forests to agriculture and animal husbandry, the species could spread to the north (7000 to 4000 BC).

It grows in dry grassy places such as meadows, garigue, heaths, and pine woodland, generally on calcareous soils.

Autumn lady's tresses may be found on quite different substrates, from weathered chalk and limestone to sand and gravel in dunes and slightly acidic heathlands.

The species occurs in different plant communities, most commonly in highly diverse Festuca ovina–Avenula pratensis grasslands that exist because of intense grazing by sheep or rabbits.

Characteristic species that may be abundant in these grasslands in the UK include the grasses Sheep's fescue Festuca ovina, red fescue F. rubra, Quaking-grass Briza media, crested hair-grass Koeleria macrantha and Crested dog's-tail Cynosurus cristatus, the dicots ribwort plantain Plantago lanceolata, Small burnet Poterium sanguisorba ssp.

In the Netherlands, the remaining population in an old dune grassland occurs in a community akin to the Botrychio-Polygaletum, where it occurs with Briza media, Glaucous sedge Carex flacca, Broad-leaved thyme Thymus pulegioides, Common milkwort Polygala vulgaris and Fairy flax Linum catharticum.

But there are also fungi present in the tubers that were not known to enter into an endophytic relationship, such as the ascomycete genera Davidiella, Leptosphaeria and Alternaria and the basidiomycete Malassezia.

The access to the nectar is very narrow to by the protruding edge of the column and the glands, and will cause the tongue of the bumblebee or bee to tear a membrane that covers the base of the two pollinia.

It seems that autumn lady's tresses responds to this preference by offering different inflorescence types and thus increases the chances of fertilization.

Because the species has little competitive strength, the soil must be moderate poor in nutrients and eutrophication, for example from adjacent farmland, should be avoided.

Therefore, acidification must be halted, on loamy soils for example by raising the ground watertable slightly, or by removing the acid humus layer.

On sandy soil, it is important to retain or restore the small scale relief so that the optimal moisture is present both in dry and in wet years in the field.