Thelymitra

Cladus: Eukaryota
Regnum: Plantae
Divisio: Magnoliophyta
Classis: Liliopsida
Subclassis: Liliidae
Ordo: Asparagales
Familia: Orchidaceae
Subfamilia: Orchidoideae
Tribus: Diurideae
Subtribus: Thelymitrinae
Genus: Thelymitra

Thelymitra is a genus of orchids known as 'sun orchids' in reference to their habit of only opening in warm weather.

Description

They are about 100 species distributed in higher rainfall areas across Australia (with 50 or so species), New Zealand (10+ endemic species), New Caledonia (2), Timor, Java, and the Philippines.

The type species is Thelymitra longifolia J.& G. Forst. 1775 from the South Island of New Zealand. The scientific name Thelymitra was given by J. R. and G. Forster, botanists on Captain Cook's second voyage. The genus name is derived from the Greek words thely (woman) and mitra (mitre hat), referring to elaborate shape of the staminodal (staminode = sterile stamen) structure at the top of the column, called a mitra.

These terrestrial orchids are only above ground during spring and early summer, usually with a single leaf, growing up from two underground tubers. It is elongated or linear-lanceolate and glabrous. The Custard Orchid (T. villosa) is the only species with a hairy leaf. The leaves of T. spiralis and T. variegata are spirally twisted.

The flower stalk is usually a bluish-green colour. The flower stem usually carries 4 to 10 flowers (even up to 20 flowers in the Plain Sun Orchid, T. holmesii), often opening all at once, though some species have only one flower each year. The flower size is between 1 and 6 cm. These flowers only open in bright sunlight (in combination with warmth and humidity), close at night and during cold or cloudy weather.

Sun orchids exhibit a particular characteristic : their lip shows, except in a few species such as T. variegata, almost the same shape, colour, colour pattern or size as the other petals and sepals. This gives a symmetrical shape to the perianth. Furthermore the lip lacks ornamentation. In other orchid genera, the lip has a distinctive shape and colour. The particular shape and color of the sun orchids mimics the flowers of lily family (Liliaceae) and the family Goodeniaceae, aiming by deceit for the same insect pollinators. The Slender Sun Orchid (T.pauciflora) only opens for a short time (or not at all) and is self-pollinating. This self-pollination is a successful strategy followed by several other species such as and T. circumsepta, T. graminea, T. holmesii and T. mucida.

Once the weather dries out the leaf shrivels away and the orchid lies as a single spherical tuber.

Sun orchids come in most colours, including purple, deep blue (T. pauciflora), white, pink, magenta, maroon, yellow (T. antennifera) and red (T. x macmillanii). Most are a single colour or have spots, a few have stronger variation and are multi-coloured. The deep blue colour, found in about 75% of the sun orchids, is of a rare kind, found only in 5 other orchid genera.

Several species are considered by the IUCN as endangered (T. epipactoides) or critically endangered (T. gregaria, T. hiemalis and T. x mackibbinii. A number of conservation measures are underway in South Australia.

Until shortly, the taxonomy of the genus was outmoded and understudied. Jeffrey A Jeanes of the Royal Botanic Gardens Melbourne has recently (2004) done a taxonomic revision, resolved several species complexes and described a considerable number of new species (see Muelleria 19; 2004)
Several Thelymitra species :2, 3, 6, 7, 8, 9

Species
Thelymitra species by Lewis Roberts.

* Thelymitra aemula Cheeseman 1919
* Thelymitra aggericola D.L.Jones 1999
* Thelymitra albiflora Jeanes 2004
* Thelymitra angustifolia R.Br. 1810
* Thelymitra antennifera (Lindl.) Hook.f. 1858 : Rabbit-eared Sun Orchid, Lemon-scented Orchid, Vanilla Orchid
* Thelymitra apiculata (A.S.George) M.A.Clem. & D.L.Jones 1989 : Fine Point Thelymitra
* Thelymitra arenaria Lindl. 1840
* Thelymitra aristata Lindl. 1840 : Giant Sun Orchid
* Thelymitra atronitida Jeanes 2000
* Thelymitra azurea R.S.Rogers 1917 : Azure Sun Orchid
* Thelymitra basaltica Jeanes 2004
* Thelymitra batesii Jeanes 2004
* Thelymitra benthamiana Rchb.f. 1871 : Bentham's Thelymitra, Leopard Orchid
* Thelymitra bracteata J.Z.Weber ex Jeanes 2004
* Thelymitra brevifolia Jeanes 2004
* Thelymitra campanulata Lindl. 1840 : Bell-shaped Thelymitra, Shirt Orchid
* Thelymitra canaliculata R.Br. 1810
* Thelymitra carnea R.Br. 1810 : Flesh-red Thelymitra
* Thelymitra circumsepta Fitzg. 1878
* Thelymitra colensoi Hook.f. 1864
* Thelymitra cornicina Rchb.f. 1871 : Horn-shaped Thelymitra, Lilac Sun Orchid
* Thelymitra cornuta Colenso 1887 (publ. 1888).
* Thelymitra crinita Lindl. 1840 : Long-haired Thelymitra, Blue Lady orchid
* Thelymitra cucullata Rupp 1946 : Cowl-carrying Thelymitra
* Thelymitra cyanapicata Jeanes 2004
* Thelymitra cyanea (Lindl.) Benth. 1873
* Thelymitra decora Cheeseman 1906
* Thelymitra dentata L.B.Moore 1968
* Thelymitra epipactoides F.Muell. 1866
* Thelymitra erosa D.L.Jones & M.A.Clem. 1998
* Thelymitra exigua Jeanes 2004
* Thelymitra flexuosa Endl. 1839 : Bent Thelymitra, Twisted Sun Orchid
* Thelymitra forbesii Ridl. in H.O.Forbes 1885
* Thelymitra formosa Colenso 1884
* Thelymitra fragrans D.L.Jones & M.A.Clem. 1988
* Thelymitra frenchii Jeanes 2004
* Thelymitra fuscolutea R.Br. 1810 : Brown-yellow Thelymitra, Chestnut Sun Orchid
* Thelymitra graminea Lindl. 1840
* Thelymitra granitora D.L.Jones & M.A.Clem. 1998
* Thelymitra gregaria D.L.Jones & M.A.Clem. 1998
* Thelymitra hatchii L.B.Moore 1968
* Thelymitra hiemalis D.L.Jones & M.A.Clem. 1998
* Thelymitra holmesii Nicholls 1932 : PLain Sun Orchid
* Thelymitra imbricata D.L.Jones & M.A.Clem. 1998
* Thelymitra improcera D.L.Jones & M.A.Clem. 1998
* Thelymitra inflata Jeanes 2004
* Thelymitra intermedia Berggr. 1877
* Thelymitra irregularis Nicholls 1946
* Thelymitra ixioides Sw., 1800 : Spotted Sun Orchid
* Thelymitra javanica Blume 1825
* Thelymitra jonesii Jeanes 2001
* Thelymitra juncifolia Lindl. 1840
* Thelymitra latiloba Jeanes (2001
* Thelymitra longifolia J.R.Forst. & G.Forst. 1775
* Thelymitra longiloba D.L.Jones & M.A.Clem.1998
* Thelymitra lucida Jeanes 2004
* Thelymitra luteocilium Fitzg. 1882
* Thelymitra macrophylla Lindl. 1840 : Large-leafed Thelymitra
* Thelymitra malvina M.A.Clem., D.L.Jones & Molloy 1989
* Thelymitra matthewsii Cheeseman 1910 (publ. 1911)
* Thelymitra media R.Br. 1810
o Thelymitra media var. carneolutea Nicholls 1943
o Thelymitra media var. media.
* Thelymitra megacalyptra Fitzg. 1879 : Large-capped Thelymitra
* Thelymitra merraniae Nicholls 1929
* Thelymitra mucida Fitzg. 1882
* Thelymitra nuda R.Br. 1810 : Naked Thelymitra
* Thelymitra occidentalis Jeanes 2001
* Thelymitra pallidiflora Jeanes 2004
* Thelymitra papuana J.J.Sm. 1934 : Papua Thelymitra
* Thelymitra pauciflora R.Br. 1810 : Slender Sun Orchid
* Thelymitra peniculata Jeanes 2004
* Thelymitra planicola Jeanes 2000
* Thelymitra polychroma D.L.Jones & M.A.Clem. 1998
* Thelymitra psammophila C.R.P.Andrews 1905
* Thelymitra pulchella Hook.f. 1853
* Thelymitra purpurata Rupp 1946
* Thelymitra rubra Fitzg. 1882 : Salmon Sun Orchid
* Thelymitra sanscilia H.S.Irwin ex Hatch (1952
* Thelymitra sarasiniana Kraenzl. in F.Sarasin & J.Roux 1914
* Thelymitra sargentii R.S.Rogers 1930 : Sargent's Thelymitra
* Thelymitra silena D.L.Jones 1999
* Thelymitra simulata D.L.Jones & M.A.Clem. 1998
* Thelymitra spadicea D.L.Jones & M.A.Clem. 1998
* Thelymitra sparsa D.L.Jones & M.A.Clem. 1998
* Thelymitra spiralis (Lindl.) F.Muell. 1865 : Spiral Thelymitra, Curly Locks
o Thelymitra spiralis var. pulchella Nicholls 1949
o Thelymitra spiralis var. spiralis
* Thelymitra stellata Lindl. 1840 : Star-shaped Thelymitra
* Thelymitra tholiformis Molloy & Hatch 1990
* Thelymitra tigrina R.Br. 1810 : Tiger-like Striped Thelymitra
* Thelymitra variegata (Lindl.) P.J.Müll. 1865 : Irregularly Spotted Thelymitra, (Austr.) The Queen of Sheba Orchid
* Thelymitra venosa R.Br. 1810
* Thelymitra villosa Lindl. 1840 : Hirsute Thelymitra, Custard Orchid
* Thelymitra viridis Jeanes 2004
* Thelymitra vulgaris Jeanes 2004
* Thelymitra xanthotricha Jeanes 2004

Natural hybrids

* Thelymitra × chasmogama R.S.Rogers 1927 (T. luteocilium × T. nuda)
* Thelymitra × mackibbinii F.Muell. 1881 (T. × macmillanii × T. nuda)
* Thelymitra × macmillanii F.Muell. 1865 (T. antennifera × T. luteocilium)
* Thelymitra × truncata R.S.Rogers 1917

Intergeneric hybrid

* xCalomitra (Calochilus x Thelymitra) (unplaced name)

Cultivation

Thelymitras can be grown in a freely draining, dense mixture with partially composted organic matter. A suitable mixture is an equal mix of 7 mm road screenings, year old composted wood chips and commercial potting mix. It is good practice to cover the surface in pine or she-oak needles to control water loss and to feed the mychorizal fungi that support the orchid.

Due to the flowers only opening in warm weather, it is common practice for showing them, to use a bank of strong incandescent lights to simulate the warm sun.

Some work has gone into growing hybrids for better growing and more colour. The most popular hybrid is probably Th. x "Kay Nesbitt" with its strongly coloured reddish pink flowers.

References

* Pamela Burns-Balogh and Peter Bernhardt (1988). "Floral evolution and phylogeny in the tribeThelymitreae (Orchidaceae: Neottioideae)". Plant Systematics and Evolution 159.
* Breiner, E. and Breiner, R. (2003). "Thelymitra, die sun orchids: eine bemerkenswerte Orchideen-Gattung aus Australien.". Orchidee 54 (3): 350–351. (in German)
* Jeans, J. A. (2004). "A revision of the Thelymitra pauciflora R.Br. (Orchidaceae) complex in Australia". Muelleria 19: 19–79.