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


Margaret Lee’s Diuris orientis and 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;


and Helen Lawrence’s 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


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.


2015 June Winning Photograph

06 sm PM Arachnorchis argocallaOf the five entries this month, four featured winter orchids. Lorraine Badger entered a Diplodium robustum, whilst Claire Chesson, Robert and Rosalie Lawrence all entered Urochilus sangineus. Though not the winning photographs it was interesting to see the differences between the U. sangineus with one being no taller than the small Acianthus pusillus next to it and another being taller than the rapier sedge.

But the winning photograph was the spring flowering Arachnorchis argocalla (White Beauty Spider Orchid) by Pauline Meyers. This is amongst our most threatened orchids and is dealt with in depth in the Recovery Plan For Twelve Threatened Orchids in the Lofty Block Region of South Australia 2010. This fungi dependent endemic orchid is rated Endangered both at State and National level.

Found in the Southern and Northern Lofty regions, it range has been severely reduced by possibly 80%. Since 1918 no plant has been found south of Adelaide.

Flowering from September to October, it is often found in grassy woodlands often growing on gentle southerly-facing hill slopes. The soil is a clay loam with a high humus content.

This beautiful orchid has one to two non-perfumed white flowers with thickened but not clubbed drooping lateral sepals and petals. The strongly recurved broad labellum is usually white, sometimes crimson, fringed with short teeth.

This is one of our larger spider orchids reaching a height of 60cms. The size of the plant flower and leaf help to distinguish it from other similar appearing orchids such as A. brumalis and albino flowers of A. behrii.

Like many of the spider orchids it takes 2 – 5 years to reach maturity and then has a potential reproductive life of 10 years. With an average pollination rate of less than 10%, the potential to increase the population is low and any threat to survival of the individual plants needs to taken seriously.

Some threats are obvious such as weed invasion including the garden escapees such as Topped lavender (Lavandula stoechas spp. stoechas) and action is being taken to curb the spread of weeds through targeted weeding programs.

Another threat is habitat loss. This has been the result of land clearing but sites are being protected either through conservation legislation or Heritage Agreements. Habitat loss can also occur indirectly and that is through Phytophthora being introduced into the sites. Although the direct effect of Phytophtora on the orchid is unknown, it is known that it can affect the plants that grow in association with this orchid. This threat can be reduced by all of us implementing good hygiene practices.

These were some of the threats noted in the Recovery Plan. This plan was not just defensive, ie attempt to halt and minimalize the damage; but it was also proactive with measures outlined to increase the population. These included seed and fungi collection eventually resulting in germination and cultivation with a view to re-introduction.

It is good to see that there is a plan and active steps are being taken to bring this orchid back from threat of extinction.

June 2015 other entrants

Photographers from L to R: Claire Chesson, Rosalie Lawrence, Lorraine Badger, Robert Lawrence


Websites accessed 1 July 2015

White Beauty Spider Orchid (Caladenia argocalla) Recovery Plan
Caladenia argocalla – White-beauty spider-orchid, biodiversity species Profile and Threats Database
Recovery Plan For twelve threatened Orchids in the Lofty Block Region of South Australia

Bates R J, South Australia’s Native Orchids 2011 DVD