Spiranthes, commonly called Ladies'-tresses, is a genus of orchids (family (Orchidaceae) belonging to the subfamily Orchidoideae.
It has a very wide, almost continuous distribution, mostly in temperate zones of the northern hemisphere: Europe, North Africa, Asia, Australia, New Guinea, the Americas and the Caribbean. It is a provincially endangered orchid, in North America it can be found in Manitoba, Ontario and more than 20 American states. They grow in meadows, fields and savannas but are also found in forests, both on acid and calcareous soil. Most species tend to become weeds in disturbed areas, while they may be scarce in undisturbed areas.
Plants can grow to a height of 12 to 38 cm (4.5 to 15 inches). Spiranthes consists of perennial, terrestrial orchids with clustered, tuberous or rarely fibrous, fleshy roots. The leaves are basal or occasionally cauline (i.e. emerging from the stem). They are variable in shape. They range from broadly ovate to elliptic, or absent at flowering.
The flowering stem has foliaceous sheaths. The stem is erect and spiraling (as the name Spiranthes indicates). It carries persistent, sheathing bracts. The resupinate, tubular flowers are arranged in a more or less spirally twisted, showy or inconspicuous terminal spike. Their color is typically a shade of white or yellowish-white or even pink ( as in Spiranthes sinensis). Flowers are pollinated by bumble bees and butterflies.
This genus has undergone many taxonomic changes : originally Spiranthes contained all the species from the subtribe Spiranthinae. In 1920 Schlechter divided this genus in 24 genera. A revision by Williams in 1951 and by Schweinfurth in 1958, inflated the number of species of this genus again. Finally D. Szlachetko, with several studies in the 1990s, divided this genus in several genera, contained in 3 subtribes. During all these changes, there is only one species that has remained taxonomically unchanged : Spiranthes parksii
Flowers of this genus are commonly popular in Japan, where it is called Nejibana (lit.twisting flower.)
Grow in moderate lighting. Plant grows in cool to cold temperatures and should be water regularly during growing season and reduced during flowering. Reduce watering during dormancy period in the winter and mist occasionally. Pot with 70% fine to medium grade perlite or clay and 30% soil, peat.
This genus is named after the spiral form the flower take on the raceme
- Aristotelea Lour. 1790
- Cyclopogon C. Presl 1827
- Cycloptera (R. Brown) Spach 1841
- Dothilis Raf. 1836-7
- Gyrostachys Pers. ex Blume 1859
- Ibidium Salisb. ex Small 1913
- Stenorrhynchos Rich. ex Spreng. 1826
- Triorchis Millan 1765
Since the species do not readily cross with each other, hybrids are rare in this genus.
- Spiranthes × eamesii P.M.Br., 2006.
- Spiranthes × intermedia Ames (1903) (SE. Canada to NE. U.S.A.)
- Spiranthes × itchetuckneensis P.M.Br. (1999) (Florida)
- Spiranthes × simpsonii Catling & Sheviak (1993) (SE. Canada to NC. U.S.A)
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- Schlechter, R. (1920). "Versuch einer systematischen Neuordnung der Spiranthinae". Beih. Bot. Centralbl. 37: 317–454. (in German)
- Williams, L.O. (1951). "The Orchidaceae of Mexico". Ceiba 2: 1–321.
- Schweinfurt C. (1958). "Orchids of Peru". Fieldiana Bot. 30: 1–260.
- Szlachetko D.L. (1996). "Studies on Spirantheae (Orchidaceae) I. Varia". Fragm. Flor. Geobot. 41: 845–863.
- Sheviak C. (1990). "A new Spiranthes (Orchidaceae) from the cienegas of southernmost Arizona". Rhodora 92: 213–231.
Spiranthes at CultureSheet.org