Orchid Basics – Labellums and Columns

Orchids are unique in the floral world. Two distinctive characteristics that set orchids apart from other plants are the labellum and the column.

The labellum is a modified petal.  It is extremely varied in appearance; “often lobed, spurred, adorned with glands, appendages of calli (callus, a hardened swelling or thickening of the skin), sometimes mobile and highly irritable and often brightly coloured”. * The labellum is important for pollination.

The column (as described by Bates and Weber) “is a distinctive feature of all orchids and a unique structure in the plant kingdom. It is formed by fusion of the male parts ‘stamens’ and female organ ‘pistil’.”*

Below are examples of the various types of labellums and columns in some South Australian terrestrial orchids. Each genus has its own characteristic labellum and column.

Sun Orchid

Thelymitra – though the labellum is almost indistinguishable from the other petals and sepals, the column is quite complex.

Hyacinth Orchid

Dipodium or Hyacinth Orchid

Greenhood

Pterostylis or Greenhoods – generally a simple labellum with the column hidden well back into the hood.

Spider Orchid

Arachnorchis (syn Caladenia) can have quite varied and complex, mobile labellums

Helmet Orchid

Corybas or Helmet Orchid – the labellum dominates and the column is hidden deep inside the flower.

Donkey Orchid

Diuris or Donkey Orchid – the labellum is divided giving the appearance of more than one structure.

*Bates and Weber Orchids of South Australia 1990

 

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2017 June Winning Picture

1706 sm RWL Thelymitra grandiflora 10

This month’s theme for the photo competition was blue and white. White flowers can occur as a result of lack of colour such as Rosalie Lawrence’s Caladenia latifolia (Pink Fairies) which is normally pink. White orchids can also occur naturally such as the Arachnorchis argocalla (White Beauty Spider Orchid) and Arachnorchis intuta (Ghost Spider Orchid) both photographed by John Fennel, or as a dominant colour such as Lorraine Badger’s Eriochilus collinius (syn Eriochilus sp Hills Woodland).

Of the blue orchids, both Ricky Egel and John Badger entered pictures of Thelymitra x truncata (Blue Spotted Hybrid Sun Orchid) whilst Robert Lawrence entered a Thelymitra grandiflora (Giant Sun Orchid) which was the outstanding winning picture.

Blue in the floral world is unusual colour in the floral world for it is not a naturally occurring colour. In fact, “[t}he key ingredient for making blue flowers are the red anthocyanin pigments. Less than 10 percent of the 280,000 species of flowering plants produce blue flowers.” (Lee, 2010 as cited in Oder 2014).

Whilst blue orchids occur outside of Australia, their “colour cannot rival” … “the intensely blue flowers” … “especially [are] unique in the orchid world” … “of their Australian counterparts. The sun orchids (Thelymitra) in particular are famous for their sky blue flowers.” (Ronse 2008: 103)

Based upon Jones 2006 tome, the following genera have true blue orchid species – Cyanicula (9 species), Pheladenia (1 species), Epiblema (1 species) and the largest group Thelymitra (about 65 out of potentially 118 species) plus one hybrid, XGlossodenia tutelata. Of the epiphytes, blue is almost non-existent except for three which Jones lists that rarely might be bluish and they are Vappodes bigibba, V. lithocola and V. phalaenopsis*.

With such rarity, is it any wonder then that the Chinese attached special significance to it as a plant that could cure lung disease and the Aztecs saw it as a symbol of strength.

*Names used as they appear in Jones 2006 tome

Reference

Jones, D. L., A Complete Guide to Native Orchids of Australia Including the Island Territories. Reed New Holland

Lee, David (2010), Nature’s Palette: The Science of Plant Color< Chicago, University of Chicago Press

Oder, T, The Science of Blue Flowers https://www.mnn.com/your-home/organic-farming-gardening/stories/the-science-of-blue-flowers accessed 6 July 2017

Pretty Zesty All About Blue Orchids http://www.prettyzesty.com/2012/11/all-about-blue-orchids.html accessed 6 July 2017

UPSIDE UPSIDE DOWN

Leo Davis always has some interesting insights from his orchid observations.  In this article he examines the position of the tepals (petals and sepals) in particular the Moose Orchid which he saw for the first time this year.

Have a close look, next season (winter to early summer) at some of our native lilies.  Start with the jolly bulbine lily (Bulbine bulbosa), no longer a true lily incidentally, because it now resides in family Aspodelaceae, along with the grass trees. You will find three yellow petals at 12, 4 and 8 o’clock and closely behind them three almost identical sepals at 2, 6 and 10 o’clock, so at first sight you see six apparently identical tepals (sepals and petals).  Move on to the rush fringe-lily (Thysanotus juncifolius), as described in Ann Prescott’s ‘It’s Blue With Five Petals’.  Clive Chesson is more up to date and tells me it is now T. racemoides.  Again it is no longer a true lily, now sitting in family Asparagaceae.  Here the tepals are noticeably different.  Three wide densely fringe edged petals will be found, if you view the flower face on, at 12, 4 and 8 o’clock.  The narrow non fringed sepals sit close behind at 2, 6 and 10 o’clock.  These are just a generalisations because if the flower turns only about 60o a sepal will be at the top.

Most orchids, while close relatives of the true lilies and the one time lilies, do not show these arrangements.  Let’s start with some that do.

In the large duck orchid (Caleana major) the petal at 12 o’clock, the dorsal petal, is modified, as in most, but as usual, not all, orchids, to become a labellum.  In this charmer the labellum takes the form of a duck’s head.  Its function is to snap down trapping a pollinator insect in the cup shape column below it, forcing it into contact with the sticky off white stigma and/or the yellow pollinia below it.  Look closely and you will find the other two narrow petals drooping at around 4 and 8 o’clock.  Two folded, twisted sepals can be clearly seen at around 1 and 11 o’clock.  The third sepal, at 6 o’clock, is tucked in behind the cup shaped column.  Note that, as with lilies, the top tepal is a petal.

ld-caleana-major

Caleana major, Knott Hill NFR Photographer: Leo Davis

The leek orchids (genus Prasophyllum) follow this pattern and also have their labellum at around 12 o’clock.  These orchid groups, which are up the right way, are said to be ‘not upside down’, using the technical term ‘non resupinate’.

Most orchids are ‘upside down’ and are called resupinate.  The whole flower rotates 180o, clockwise or anti I don’t know, at the embryonic stage.  But let’s start with somewhat of an exception with the sun orchids (genus Thelymitra) which do not have a petal modified as a labellum.  But they are indeed upside down.

Have a close look at the Thelymitra benthamiana flower.  Note that the three petals, at roughly 2, 6 and 10 o’clock, are in front of the three slightly larger but very similar sepals, at 12, 4 and 8 o’clock.

Note that the top tepal is a sepal.  The flower is upside down, that is resupinate.  In most orchids the petal at 6 o’clock would be modified to be a labellum.

ld-thelymitra-benthamiana

Thelymitra benthamiana, Scott Creek CP; Photographer: Leo Davis

The Arachnorchis (possibly Caladenia to you) stricta, from Sherlock, out in the mallee, is more typical of terrestrial orchids in SA.  It is upside down, that is resupinate, and has a petal modified to be a labellum.

The bottom petal has become a wide labellum, with fine edge combs and parallel rows of rich plum coloured calli covering its centre.  Out at roughly 3 o’clock is a narrow petal, the other invisible on the other side.  At the top, pressed tightly against the column, a sepal arches forward.  Two larger sepals extend down at around 5 and 7 o’clock.

ld-arachnorchis-stricta

Arachnorchis stricta, Sherlock; Photographer: Leo Davis

When I saw my first, my only, moose orchid, this season, I was in such a state of excitement that it looked to me to be up the right way, that is to say upside down.

ld-cryptostylis-subulata

Cryptostylis subulata, Stipiturus CP; Photographer: Leo Davis

Have a look.  Two narrow short roughly vertical petals at about 1 and 11 o’clock.  There are two sepals at just past 3 and just before 9 o’clock. That’s OK but where is the other sepal?  Are there it is, where it should be, at midday.  But hang on, it’s behind the flower stem (peduncle) and where is the column?

ld-cryptostylis-subulata-with-labellum

Cyrtostylis subulata with labellum lifted; Photographer: Leo Davis

Holding the labellum up with a stick I found the column, the stigma and the pollinia, underneath the labellum.  The third sepal now appears to be at 6 o’clock.  And it all became clear.  This flower was up the right way (non resupinate) but it has turned forward, on its peduncle, by about 180o, to become upside down, but not in the manner of resupinate flowers, because it is back to front.  It is an inverted non resupinate flower.  Still with me?

2016 Orchid Picture of the Year

For the final meeting of the year we chose the best of the 2016 monthly winners of the picture competition.

Here in Australia we are fortunate to have such a variety of orchids. They may not be as big and showy as some of the overseas orchids but the diversity of shapes fires the imagination as reflected in this year’s monthly winners, when put together. The common names of the winners – spider, leopard, flying duck, cowslip, zebra, helmet, bluebeard and greenhood – reinforce this theme of diversity.

Patterns and colours contribute to the variety of our orchids. Australian orchid colours run the gamut of the rainbow and more, with Australia being home to most of the naturally occurring blue orchids in the world. This colour fascinates and allures people around the world so much so that nurseries will dye a white orchid blue because it will sell. There is even a website devoted to the colour called, not surprisingly, Blue Orchid  and the popular band master Glenn Miller wrote a song titled Blue Orchids (1944).

Could this be why the very clear winner for the year was Claire Chesson’s Pheladenia deformis common name Bluebeard or Blue Fairy?

  congratulations-clipart-k15686507

  Claire Chesson on your most beautiful picture.

1608-sm-cc-pheladenia-deformis

Pheladenia deformis

Claire won the August competition.

As a reminder, below are the other winners for the year.  Click on the image to see the related articles.

February 2016 Photographer: Pauline Meyers

1602 sm PM Caleana major

Caleana major

March 2016 Photographer: Judy Sara

1603 sm JS Arachnorchis sp

Arachnorchis sp. (Green Combed Spider Orchid

April 2016 Photographer: Claire Chesson

1604 sm CC T benthamaniana

Thelymitra benthamiana

May 2016 Photographer: Pauline Meyers

1605 sm PM Caladenia flava

Caladenia flava

2016 June Photographer: Ros Miller

1606 sm RM Caladenia cairnsiana

Caladenia cairnsiana

2016 July Photographer: Robert Lawrence

1607 sm RWL Corysanthes diemenicus

Corysanthes diemenica (mutation)

2016 September Photographer: Bevin Scholz

1609-sm-bs-pterostylis-cucullata

Pterostylis cucullata

2016 October Photographer: Helen Lawrence

1610-hl-sm-arachnorchis-argocalla

 

2016 October Winning Picture

 

Quite a few pictures were entered this month.

Ricky Egel’s Thelymitra x irregularis, 1610-re-sm-thelymitra-x-irregularis

Pauline Myer’s Caladenia falcata and Caladenia carinsiana; 1610-pm-sm-caladenia-falcata

1610-pm-sm-caladenia-cairnsiana

Margaret Lee’s Diuris orientis and Nemacianthus caudatus;

1610-ml-sm-diuris-orientis

1610-ml-sm-nemacianthus-caudatus

Judy Sara’s Arachnorchis tensa;

1610 JS A4 Arachnorchis tensa.jpg

Greg Sara’s Arachnorchis stricta which had an unusual green coloured flower;

1610-gs-sm-arachnorchis-stricta

and Helen Lawrence’s Arachnorchis argocalla.

1610-hl-sm-arachnorchis-argocalla

Helen’s picture of the nationally endangered A. argocalla was the outstanding winner.  Now known as the White Beauty Spider Orchid^, it was featured last year as a winner with Pauline Meyer’s June 2015 entry*.

This is one of our largest spider orchids. For size, beauty and delicacy it rivals the Western Australian Caladenia longicauda ssp. eminens (White Stark Spider Orchid) and A. venusta, syn. Caladenia venusta (Graceful Spider Orchid) from Victoria and the South East.

It shares many similarities with these two species in that they are reasonably good size white flowers with a stiffly hinged labellum that has long, thin teeth and the segments have threadlike tips without clubs.  It is separated both geographically and in the type of habitat from these two species. A. argocalla is a plant of the inland hills and valleys.

Though primarily a white flower and part of the A. patersonii complex, A. argocalla has red colouring in the labellum which according to Backhouse may possibly indicate genetic introgression (that is long term mixing of the gene pool) with either the A. reticulata or A. leptochila complexes. Certainly, the colour of the labellum was quite variable ranging from white through to a deep red.

^Previously known as Common White Spider Orchid because of its abundance but now only known to a limited number of locations.

*NOSSA Journal, July 2015

Reference:

Department of the Environment (2016). Caladenia argocalla in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Thu, 3 Nov 2016 16:31:39 +1100

Introgression https://en.wikipedia.org/wiki/Introgression Accessed 4 November 2016

Bates, R. J., ed. (2011). South Australian Native Orchids. Electronic version, 2011. NOSSA

Jones, David L (2006) A complete Guide to Native Orchids of Australia, Frenchs Forest, NSW: Reed New Holland

Backhouse, G (2011) Spider-orchids the Genus Caladenia and its Relatives in Australia

 

NB: November Competition will be judging the monthly winners from this year.

Orchid Hunter Visits Kuipto

The following video is by Orchid Hunter, Julian Pitcher.  Julian is concerned about the conservation of orchids and is also keen to teach others about Australia’s unique orchids.  At the time of the visit, Julian was resident in Victoria; now he resides in Queensland.  Enjoy an interstate visitor’s view of our beautiful orchids.

Culture of Fungi Dependent (FD) Terrestrials

This is the last of the three terrestrial fact sheets in Culture Notes that NOSSA has produced on growing terrestrial orchids.  All three facts sheets can be downloaded – Click on the following for Fungi Dependent, Slow Multipliers and Fast Multipliers.

Orchid 1 Arachnorchis tentaculata

Arachnorchis tentaculata, common name King Spider Orchid or Large Green Comb Spider Orchid

FLAGBEARER SPECIES: Caladenia tentaculata (synonym Arachnorchis tentaculata)

Some 3/4 of Southern Australian terrestrial orchids are fungus dependent throughout their life cycle. Orchids that are fungus dependent have very specific cultural requirements. The fungus must be grown in the pot with the orchid. Sometimes a third entity such as a shrub or tree is involved in the fungal relationship.

A minimum disturbance culture is used.

Limited numbers are available each year. Other fungus dependent species are rarely available. Those in cultivation have mostly come from rescue digs in the past. NOSSA has started a seed kit project to help overcome this vacuum.

GROWTH HABIT: Australian ground orchids follow an annual growth cycle comprising 6 – 8 months as growing plants under cool (5 – 20°C max, 0 – 14°C min) moist conditions and 4 – 6 months as dormant tubers in hot dry (18 – 42°C max, 12 – 30°C min) conditions. The new tuber is produced in winter – spring. Each tuber sends up a shoot to the surface in Autumn and leaves grow rapidly in late Autumn/early Winter as temperatures fall and the rains set in. Sometime in October/November the leaves go yellow and then brown and dry as the days get longer, hotter and drier in late Spring.

LIGHT/SHADE: In Adelaide they thrive in a shadehouse of 50% shadecloth. Some species prefer heavy shade, others full sunlight, but most will adapt to a wide range of light intensity.

If the leaves and stems are weak and limp or if the leaf rosettes are drawn up to the light then the shading is too dense and the amount of light should be increased. FDs are mostly spring flowering and like higher light intensities at flowering time. flowers may have pale colours if placed in heavy shade, even temporarily, when buds are just starting to open.

In very cold areas an unheated glasshouse may be required for frost protection although light frosts do not worry the majority of species.

AIR MOVEMENT/HUMIDITY: All species like good air movement and will not thrive in a stuffy humid atmosphere especially if temperatures are high.

POLLINATION/SEED COLLECTION: FDs seldom multiply so must be propagated from seed.

Flowers on the strongest plants of the same species growing in pots are cross pollenated by hand to set seed pods. The flowers collapse in a day of so and pods ripen in 4-8 weeks. Pods are collected as they change colour from green to brown, which happens quickly on a hot day in October/November. Tea bags can be tied over the pods to catch the dust like seed if frequent visits to site are not possible.

Pods are stored dry in paper envelopes indoors over summer. Seed can be sprinkled on mother pots or scattered on bush sites.

SEEDLING CARE: Seedlings can be raised by sowing seed around potted mother plants.

At Easter time, just before the rainy season begins, the dust-like seed is mixed with fine sand in a pepper shaker (minimizes seed loss) and sprinkled on top of the pots and watered in. Germination occurs in Autumn/Winter as that is when the fungi are most active. Tiny leaves appear from July to October. The seedlings form miniscule tubers on droppers about 1 – 2cm below the surface. Seedlings take up to five years to reach flowering and are best left undisturbed until larger.

WATERING: The soil should be kept moist at all times during active growth by watering gently if there is no rain. Hand watering is especially necessary in spring as soil in pots dries out more rapidly than in the garden. Watering must be done slowly so that the mat of needles on the surface of the pot is not disturbed. Slugs and snails love these plants and must be kept under control. Raising the pots off the ground on galvanised steel benching is very effective in controlling these pests.

After the leaves have turned yellow, let the pot dry out completely to dry up the old roots and tubers otherwise they may turn into a soggy mouldy mess and rot may destroy the adjacent new tubers.

REPOTTING: The plants are not repotted but left in the same pot year after year.

SUMMER CARE: Keep the pots shaded and allow the pots to dry out between light waterings until mid-February when they should be set out in their growing positions and watered a little more often. The tubers of some species will rot if kept wet during the dormant period, others will produce plants prematurely which are then attacked by pests such as thrip and red spider and fungal diseases in the warm weather.

A thin layer of new leaf litter is placed on top of the existing leaf litter each summer to feed the fungus.  Chopped gum leaves or sheoak needles are suitable.

FERTILIZING: NO FERTILISER

OTHER CULTURE NOTES:

March 2016 Winning Photograph

1603 sm JS Arachnorchis sp

We frequently receive entries from Western Australia but this month our entries were from both the west and the east. Allen Jennings entered a Calanthe triplicata (Christmas Orchid) from New South Wales. Pauline Meyer’s was from the west, (Western) Flying Duck Orchid, Paracaleana nigrita. The other entries were South Australian, Jenny Pauley’s recently photographed Leporella fimbriata (Fringed Hare Orchid), Greg Sara’s Thelymitra rubra (Common Pink Sun Orchid) and Judy Sara’s Plumatochilos sp. (Bearded Orchid) and Arachnorchis sp. (Spider Orchid).

The winning photograph was Judy’s Spider Orchid. Obviously it was one of the Green Comb Spider Orchids – A. dilatata complex. Of this group there are about a dozen possibilities. Knowing the location, Mt Boothby, helped to narrow the options with the most likely candidate being Arachnorchis stricta but it wasn’t convincing. It would appear that the tips of the sepals may have been chewed off when in bud.

A distinguishing feature of this species is that there are no clubs or osmophores on the sepals. Other species of this complex have clubs. Another feature is that the dorsal sepal is bent over the column unlike many other green combs which have an erect dorsal sepal. The features that caused doubt were lateral sepals looking droopy instead of being characteristically stiffly held out but dry conditions could cause this. The other was that the labellum did not strictly fit the description of A. stricta but then again it is a variable species.

The conclusion was a possible hybrid but there is no information on the likely parents or that is an atypical A. stricta that may have been damaged in bud.

This is an example of the difficulties that can occur when attempting to identify a plant from one photograph.

Reference:

Personal communications Thelma Bridle (NOSSA Conservation Officer)

Personal communications Bob Bates

Bates, R. J., ed. (2011). South Australian Native Orchids. Electronic version, 2011. NOSSA

Rules of entry:

The subject matter must have something to do with Australian orchids.  Any format is acceptable including Photo shopped images, artwork, etc

How to enter:

Email nossa.enquiries@gmail.com – jpg as large as you are able to send it, preferably A4 ratio for printing

Post: PO Box 565, Unley, 5061

Bring in to the meeting

It’s Not Extinct at Ferris-McDonald After All

Leo Davis is an enthusiast about the natural world and shares his knowledge through different journals.  He is a keen observer and meticulous in his record keeping.  He is also very knowledgeable about orchids.  The following is one such article of Leo’s.

GOOD NEWS FROM FERRIES-McDONALD CONSERVATION PARK
Leo Davis

I was aware of the Star Spider Orchid from Bates who lists the species as ‘3E, critically endangered in South Australia, nationally rare’ (pp. 242–243). I knew that in the past it had been found at Monarto and Hartley and discussions with members of the Native Orchid Society of SA (NOSSA) suggested that it had been seen at Ferries-McDonald Conservation Park, but was now possibly extinct there. My searches over five years had all failed.
On August 2, 2014, I ran into, then strangers, Len Stephens and his grandson Rickey Egel, in Monarto C.P. They had just come from Ferries-McDonald C.P., about 8 km further south. Rickey, who has a very good eye for spotting orchids, showed me an image, in his camera, of ‘the common spider orchid’. From my hurried glimpse I knew immediately it was far from ‘common’ and told him so. I headed straight for Ferries-McDonald C.P. for the first of many fruitless searches.  On August 14, 2015 Rickey and Len showed me a few Star Spider Orchids in flower at Ferries-McDonald C.P. Because I was to lead the Botany Group of the FNSSA on an outing to Ferries-McDonald C.P. on September 5, I had been visiting the park almost weekly and so was able to spend many hours looking for the orchid. It is difficult to spot, being quite small. This year’s plants, perhaps not typical given the very dry June, are between 8 and 20 cm high with flowers only about 35 x 30 mm.
Plants were only found in Broombush (Melaleuca uncinata) associations. As soon as Eucalyptus species were present the orchid was no longer found.
Any survey, especially by a single person, will produce a lower count than the actual population. Leaves of non-flowering or beheaded (the fate of so many spider orchid flowers) plants will not be recognised, some flowers will not be spotted and some plants will flower before or after surveys, with some areas surveyed on different days. Between August 14 and September 5, 2015 just 18 flowering plants (Fig. 1) were positively identified (about the same number of likely leaves and buds, adjacent to these, were noted) over a narrow area of approximately 3,000 m2. The area searched was very much greater than this. Small as this tally is, it establishes a significant population other than the only other South Australian one that I know.  That is on the private property of farmer […], at Hartley. With his kind permission I have counted over 100 flowering plants there during five visits from July 28 (buds only) to August 30 (Fig. 2). The actual population will be larger because I did not cover all of that location. My observations suggest the populations I know to be around 150 to 200 plants with other occurrences probably existing around Monarto and Hartley.
Why have I avoided the scientific name? Many of you will follow the Electronic Flora of South Australia which lists the Star Spider Orchid as Caladenia stellata, as does Backhouse (pp. 456–457). I prefer to follow Jones (p. 76) (who does not recognise the species occurring in SA) and Bates (p. 242) (who says it does occur in SA), both of whom call it Arachnorchis stellata. Backhouse points out that the nearest other occurrence, the major one, is in central southern New South Wales, south of Rankin Springs, several hundred kilometres away, and that the plants there differ from our populations in having smaller flowers. He suggests that we are looking at a separate undescribed species, Caladenia sp. ‘Murray mallee’ (p. 484), but that it might indeed be co-specific with the Rock Star Orchid (sic), Caladenia saxatilis, which is similar and occurs further north, in the northern Mt Lofty and the southern Flinders Ranges. Bates told me in conversation, that he disagrees with Backhouse and believes the local plants are the same as those in NSW and distinct from A. saxatilis, which grows in soils of different pH (acidity).

 

Good News from Ferries-McDonald-1 38LD

Fig 1: Arachnorchis stellata, Ferries-McDonald CP,  August 22, 2015.  Photo: Leo Davis

Good News from Ferries-McDonald-2 38LD

Fig 2: Arachnorchis stellata Hartly, South Australia, August 5, 2015.  Photo: Leo Davis

BIBLIOGRAPHY:

Backhouse, G. (2011). Spider-orchids – the genus Caladenia and its relatives in Australia. DVD/pdf, Backhouse, Melbourne.
Bates, R.J. (2011). South Australia’s Native Orchids, DVD, NOSSA, Adelaide.
eFlora SA. Electronic Flora of South Australia; last updated August 22, 2015.
Jones, D.L. (2006). A complete guide to native orchids of Australia including the island territories. Reed New Holland, Sydney.

 

 

Used by permission, extract from The South Australian Naturalist Vol. 89 No 2 July-December 2015.

Are there any orchids growing in the desert?

Think of deserts and the image is that of a bleak barren landscape with little to see but this is not so.  The conditions are harsh but there is a myriad, though not an abundance, of hardy fauna and flora if one but looks closely.

But concerning orchids – No orchids have been found in true deserts…..  They also appear to be absent from the arid mountains of the far north-west, or at least no-one has ever found orchids there.

Orchids need moisture and so they do not grow on unstable soils such as dry sand-hills, gibber plains or the many saline areas of the far north but on the desert fringes there are micro-climates where the moisture, humidity and soil structure is  just right (to quote Goldilocks) for orchids.  This micro-climate is created by [s]hrubland  [which] is … [an] … important dryland orchid habitat. Besides providing shade and shelter for the orchids, shrubs like the many species of wattles, Acacia and hop-bush Dodonea drop fine leaves which help to hold the soil together and slowly break down into humus rich with nutrient and water storing capability. These shrublands usually form in soils too dry or shallow for trees. Orchids of course have no need for deep soils as they are shallow rooted. 

Robert Bates Semi-arid Shrubland.jpg

Semi-arid Shrublands, Flinders Ranges

Of the five desert botanical regions, the Eastern region contains the most number of species with over a dozen species.

Botanical Regions Map

Colour added to indicate the desert regions (in red)

Orchids of the Eastern Region – this region is from the east of the Flinders Ranges to the New South Wales border and includes the Olary Spur and Lake Frome.

Arachnorchis toxochila – Dry Land Spider Orchid or Bow Lip Spider Orchid.
Corunastylis tepperi – Mallee Midge Orchid
Diplodium robustum – Common green shell-orchid.
Hymenochilus pagophilus – Mountain Shell-orchid
Microtis eremaea – Desert onion orchid
Microtis frutetorum – Common woodland onion orchid.
Oligochaetochilus bisetus species complex, Rusty rufous-hoods

Oligochaetochilus sp. Blue-bush Plain – Blue Bush rufous-hood (O. bisetus complex)

Oligochaetochilus sp. Outback – Outback rufous-hood (O. bisetus complex)

Oligochaetochilus cobarensis – Little desert rufous-hood
Oligochaetochilus sp. Crossed Sepals Bibliando rufous-hood. (O. hamatus complex)
Oligochaetochilus sp. Bimbowrie Bimbowrie Rufoushood (O boormanii complex)
Oligochaetochilus linguus – Swept-back Rufoushood

Oligochaetochilus sp. Old Boolcoomatta Large-lip rufous-hood (O. linguus complex)

Oligochaetochilus sp. Quartz – Quartz hill rufous-hood (O. linguus complex)

Oligochaetochilus sp. Slender desert – Slender Desert rufous-hood (O excelusus complex)
Undescribed not within any other Oligochaetochilus complex

Oligochaetochilus sp. Canegrass – Desert Sand-hill Orchid.

Oligochaetochilus sp. Oratan Rock – Diminutive rufous-hood

Oligochaetochilus sp. ‘Mt Victoria Uranium Mine’ – Uranium rufous-hood

Prasophyllum odoratum – Scented Leek-orchid

Prasophyllum sp. Desert Desert Leek-orchid (P. odoratum complex)

The Gairdner-Torrens region includes, besides the salt lakes it is named after, the Gawler Ranges and the southern part of the Great Victoria Desert.  Though not as many species as the Eastern region, it contains some different species including a Sun Orchid.

Thelymitra megcalyptra

Thelymitra megcalyptra

Arachnorchis interanea – Inland Green-comb Spider Orchid
Arachnorchis toxochila – Dry Land Spider Orchid or Bow Lip Spider Orchid.
Hymenochilus pagophilus – Mountain Shell-orchid
Hymenochilus pisinnus – Tiny Shell-orchid
Jonesiopsis capillata – Pale Wispy Spider Orchid
Linguella sp. Hills nana – White haired little-greenhood.
Microtis eremaea – Desert onion orchid
Oligochaetochilus ovatus – Ovate Lip Rufoushood
Oligochaetochilus xerophilus – Desert rufous-hood
Prasophyllum sp. Desert Desert Leek-orchid (P. odoratum complex)
Thelymitra megcalyptra – Scented or Dryland Sun Orchid

Third of this group is the Nullabor region.  Consisting of flat treeless limestone plains, this area, surprisingly, has two species both of which have been found close to the coast.

Urochilus sanguineus – Maroon banded greenhood
Corunastylis sp. Intermediate – Halbury Midge Orchid (C. rufa complex)
Urochilus sanguineus

Urochilus sanguineus

The final two regions Lake Eyre and North-Western contain the vast expanses of desert of the far north of South Australia.  Definitely not a place to find orchids yet one specimen has been collected from each of these two regions.

Oligochaetochilus sp. Everard Range (L. Scott 173), Mimili Orchid (possibly O. woollsii complex) from North-Western Region.

Oligochaetochilus sp. Gammon Range (O excelusus complex) from the Lake Eyre region.

It is unusual to find orchids in the desert because they only grow when there have been good winter rains which isn’t very often.  But nevertheless, here in South Australia we have over 20 possible species – an astonishingly high number for such a harsh area!

Reference:

Bates R J ed, South Australia’s Native Orchids, 2011 Native Orchid Society of South Australia

Map adapted from Flora of South Australia, Fourth Edition, 1986