Banded Greenhoods Bundled Together

Here in South Australia we often have only one or two species of a complex or a genus but this is not necessarily the case in the rest of the country. One such instance is Urochilus sanguineus (syn Pterostylis sanguinea) or Maroon Banded Greenhood. It is possible that we may have a subspecies or possibly the Mallee form but nothing like the occurrence of  this species in Western Australia where it is but one of many in a complex of several – the Pterostylis vittata complex or Banded Greenhoods*.

Below, with permission, is Andrew Brown’s post on Facebook with notes and images about the complex as it is understood in Western Australia.

The Banded Greenhood complex in Western Australia

Members of this complex grow 150 to 450 mm high and have up to 20 green, brown or reddish-brown white banded flowers characterised by their, short, broad lateral sepals which are joined at the base and a small, insect-like labellum which flicks up when touched. In all species, flowering plants lack a basal rosette of leaves while non-flowering plants have a flattened, ground hugging, rosette of leaves.

Banded greenhoods are found over a wide geographic range between Binnu north of Geraldton and Eyre on the Great Australia Bight, growing in shrublands, woodlands, forests and shallow soil pockets on granite outcrops.

There are ten Western Australian species in this complex, seven of which are formally named. However, as two were named as species of Urochilus, a genus not recognised in Western Australia, only five of these names are currently recognised here. In Western Australia, all members of the complex are considered to be in the genus Pterostylis.

All are winter flowering.

Pterostylis concava

Pterostylis concava AB

Distinguished from other members of the complex by its prominently cupped lateral sepals and the upturned projection near the base of the labellum. Found between Bindoon and Mt Barker.

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Pterostylis crebriflora

Pterostylis crebriflora AB.jpg

Distinguished from the similar Pterostylis sanguinea by its often shorter stature and slightly larger flowers which are crowded in a dense spike near the top of the stem. Found on the Darling Scarp near Perth.

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Pterostylis sanguinea

Pterostylis sanguinea AB.jpg

A very common species that is also found in South Australia, Tasmania and Victoria. It was named from specimens collected in South Australia. The species is similar to Pterostylis crebriflora but is usually taller with smaller, more widely spaced flowers. Flower colour is variable and it is not uncommon to find brown and green flowered forms growing alongside one another. Found over a wide area between Mullewa and Eyre on the Great Australian Bight.

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Pterostylis sanguinea (Mallee form)

Pterostylis sanguinea mallee form AB.jpg

An unnamed member of the complex distinguished from Pterostylis sanguinea by its short stature and few flowered inflorescence. Found over a wide range from the Stirling Range to the north of Esperance.

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Pterostylis sp. Coastal

Pterostylis sp coastal AB.jpg

Some consider this to be a form of Pterostylis sp. small bands but it is usually taller with more widely spaced flowers. The sepals are also narrower and often slightly cupped. Found mostly in near coastal areas between Dongara and Bunbury. Similar looking plants have also been found further inland between Brookton and Mt Barker.

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Pterostylis sanguinea (green flowered form)

Pterostylis sanguinea green flowered form AB.jpg

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Pterostylis sargentii

Pterostylis sargentii AB

A common, widespread species, distinguished from other members of the complex by its smaller flowers and fleshy, tri-lobed, frog-like labellum. Found over a huge geographic range between Northampton and Mt Ney, north of Esperance.

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Pterostylis sp. Crowded

Pterostylis sp crowded AB

 

A widespread species named Urochilus atrosanguineus in June 2017. Distinguished from the similar Pterostylis sanguinea by its more robust habit and larger dark reddish-brown flowers. It is also similar to Pterostylis crebriflora but generally flowers earlier and has more widely spaced flowers in a longer spike. Found between Wongan Hills and Katanning with rare, scattered populations on the Swan Coastal Plain.

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Pterostylis sp. Eyre

Pterostylis sp Eyre AB

A distinctive member of the complex distinguished from others by its pale coloured flowers. Like Pterostylis sanguinea (mallee form) it has a short stature and few flowered inflorescence. Found along the coast between Toolinna Cove and Eyre on the on the Great Australian Bight.

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Pterostylis sp. small bands

Pterostylis sp small bands AB

A northern species named Urochilus orbiculatus in June 2017. It is regarded by some researchers to be a form of Pterostylis sp. coastal but is usually shorter with a more densely crowded spike of flowers. Its sepals are also broader, more rounded and flattened rather than slightly cupped. Found north of Perth between Cataby and Binnu.

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Pterostylis vittata

Pterostylis vittata AB.jpg

A widespread species distinguished from other members of the complex by its less fleshy, paler coloured, predominantly green flowers and narrower, elongated, slightly cupped sepals. The flowers also have a more translucent appearance. The typical form is found between Bindoon and Balladonia. There is a northern form with a shorter spike of often fawn coloured flowers found between Cataby and Binnu.

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It should be noted that in South Australia and Victoria U. sanguineus was originally called P. vittata but that species is now recognised as being endemic to Western Australia.

*As an aside, the common name Banded Greenhoods is used in South Australia for the subgenus Bunochilus (previously Pterostylis longifolia which is now considered endemic to New South Wales).

 

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2017 July Cultural Notes

Steve Howard regularly writes orchid cultural notes for various orchid clubs in South Australia. His notes are tailored specifically conditions in Adelaide. The following are his notes for both epiphytes and terrestrials for the month of July.

Epiphytes

  • Water mounted native epiphytes daily; pots weekly and small pots twice weekly depending on the weather. Hot cold types require drier conditions. Generally none to once monthly for me.
  • Colder weather slows down their metabolism in winter. Foliar feeding is beneficial.
  • Keep water out of new growths to avoid rot. Clones prone to this need to be moved under hard roof cover to keep drier.
  • Check under leaves for scale.
Epiphytes in flower (1)

Annual NOSSA Spring Show

Terrestrials

  • Weed pots as the weeds appear and ensure that they don’t get too wet.
  • Remove rotted growths.
  • Start baiting for slugs and snails as spikes emerge from protective sheaths.
  • Provide hard cover during wet weather to stop botrytis spotting and rotting out spikes.

Thelymitra plants in pots

2017 May Winning Picture

Corunastylis morrisii @ Simpson 25/2/2017

May’s theme was miniscule, or less than 10mm. Of the eight entries five were Corunastylis, two Spider orchids from Western Australia and one an epiphyte. The flowers of the two spiders, Caladenia pachychila (photographer Rob & Jenny Pauley) and Caladenia bryceana subsp. bryceana (Pauline Myers) were the largest of the group being about 10mm across whilst the Bulbophylum globuliforme (Ros Miller) and C. despectans (Rosalie Lawrence) were the smallest being only 2mm across.

Of the remaining Corunastyllis entries the flower size ranged from 3mm for C. pumila (Rob & Jenny Pauley), 4mm for C. tepperi (Ricky Egel), 7mm for C. ciliata (Rosalie Lawrence) and 8mm for C. morrisii (Rob & Jenny Pauley).

The winning picture C. morrisii (Bearded or Hairy Midge Orchid) is one of the larger midge orchids. Other synonyms are Prasophyllum morrisii and Genoplesium morrisii. This common species is mainly found in Victoria but it does extend into southern New South Wales in the east and in the west just spills 50 km over the border into South Australia where it is rated endangered. It also occurs in the south east of Tasmania.

Flowering Times: Nov – May

 
 State N D J F M A M
Tas        
NSW      
Vic
SA          √

With such a wide distribution range, it is not surprising to see quite a variation in flowering time from late spring through to autumn depending upon location.

Reference

http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Genoplesium~morrisii

https://en.wikipedia.org/wiki/Caladenia_pachychila

https://en.wikipedia.org/wiki/Caladenia_bryceana_subsp._cracens

http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Genoplesium~pumilum

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

Wapstra, M., Roberts, N., Wapstra, H. & Wapstra, A. (2012). Flowering Times of Tasmanian Orchids: A Practical Guide for Field Botanists. Self-published by the authors (May 2012
version).

Backhouse, G., Kosky, B., Rouse, D. & Turner, J. (2016). Bush Gems: A Guide to the Wild Orchids of Victoria. Self-published by the authors

2017 April Winning Picture

1704 LN Diuris behrii sm

April’s theme was yellow and orange. All of the entries proved to be spring flowering. There were several Diuris. Claire Chesson, Rob Pauley and John Fennel all entered D. orientis; Les Nesbitt and Rob Pauley D. behrii and Pauline Meyer D. corymbosa from Western Australia. Pauline also entered Caladenia caesaria subsp. maritima and John Thelymitra benthamiana.

The winning picture was Les Nesbitt’s D. behrii (Cowslip Orchid) which occurs in Victoria, New South Wales, Australian Capital Territory whilst in South Australia it is rated as vulnerable.

Les Nesbitt has been working on a recovery project of these orchids for Hillgrove Resource’s flagship, the Kanmantoo Copper Mine, located almost 55 KM from Adelaide. As this orchid is often mentioned in NOSSA Journals, it might be worthwhile looking at the person after whom this species was named.

First collected by German born Dr Hans Herman Behr (1818 – 1904) who first visited* South Australia in 1844 when the colony was barely 8 years old. During his two years in South Australia he became the first person to systematically study our botany and entomology sending reports and samples back home. The results of his observations were published in various journals, and many of his collections were named and described by other botanists including his friend, Diedreich von Schlechtendal (1794 – 1866) who named Diuris behrii after Hans.

Hans Behr was an interesting man. A man of many aptitudes; medical doctor, entomologist, anthropologist, botanist, duellist, socialist, poet, novelist, linguist, member of the Bohemian Club of San Francisco and a man of wit. From the many reminiscences written about him, it would appear that he was a likeable gentleman and a generous teacher.

Unfortunately, not everyone liked him because “he was a sworn enemy of all scientific humbug, of quacks and false pretenders” and “he never refrained from expressing his opinion of them, quite regardless of person or station” but his humour shone forth in dealing with them. Once he named a “particularly obnoxious louse” after one of his enemies.

Behr revisited South Australia in 1848 during which time he became acquainted with German-Australian botanist, Ferdinand von Meuller. He maintained friendship with many of the scientific men of the time including Ferdinand Mueller and it was through this friendship that many Australian plants were introduced into California where Behr later settled after his travels.

Though the study of butterflies was his first and enduring love, he is remembered and honoured in Australia for his botanical interests. Of the twenty-two plants named after Behr, two are orchids: Diuris behrii and Arachnorchis behrii (synonym Caladenia behrii).

*The Journal incorrectly stated that he visited South Australia with his friend, Diedreich von Schlechtendal. This did not happen. As far as I am aware Schlechtendal did not visit South Australia.

Reference

https://archive.org/details/doctorhansherman00cali

https://archive.org/stream/jstor-1630874/1630874_djvu.txt

https://en.wikipedia.org/wiki/Hans_Hermann_Behr

https://www.anbg.gov.au/biography/behr-hermann.html

Kraehenbuehl, D. N., Dr HH Behr’s Two Visits to South Australia in 1844-45 and 1848-49, J. Adelaide Bot. Gard. 3(1): 101 – 123 (1981)

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

2017 March Winning Picture

As part of 40th NOSSA anniversary, the theme for this month was Leptoceras menziesii (Hare Orchid or Rabbit Ears). Entries were received from John Badger, Pauline Meyers, Robert and Rosalie Lawrence, with John Badger’s being declared the winner.

1703 sm JB Leptoceras menziesii

In February 1978, it was announced that the nascent NOSSA society required an emblem. Members were invited to send in drawings, to be judged by members and then ratified by the committee. Mrs Chris Butler (Ron Robjohns’ daughter) was the winner. The first Leptoceras menziesii flowers to be benched at a NOSSA meeting were in September 1978. It appears to be an easy plant to grow but a most difficult one to flower.

This seems to be because it is fire dependent. In spring, it will flower profusely if there has been a summer fire such as occurred after the 2015 Sampson Flat (SA) fires. It is possible that the gas ethylene produced during a fire event may initiate the flowering response.

Otherwise, apart from the occasional flowering plant, it will be mainly leaves that are found when out in the field. The single leaf of this plant lying prostrate along the ground is distinctive. It is firm, boat-shaped, glabrous (no hairs), with a fine ‘snake-skin’ pattern. Interestingly, sterile plants can be mistaken for a plant with a developing bud as there will be at the leaf base a ligule (a thin membranous growth, often found on grass stems).

 

Reference

Backhouse, G, et al (2016) Bush Gems: A Guide to the Wild Orchids of Victoria Electronic version

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

Lawrence, R. W., (2011) Start With The Leaves

NOSSA Journal Volume 2 No 6 July 1978

NOSSA Journal Volume 2 No 9 October 1978

2017 February Winning Picture

1702 sm CC Cryptostylis subulata

The first competition for the year followed a wet orchid theme with three of the orchids being South Australian swamp orchids and the fourth from Western Australia; though not a swamp dweller, it grows in shallow moist soil.

The outstanding winner was Claire Chesson’s Cryptostylis subulata, followed by Robert Lawrence’s Spiranthes alticola, Rosalie Lawrence’s Pterostylis falcata and Pauline Meyer’s Thelymitra villosa.

Known to South Australian’s as the Moose Orchid, elsewhere it is either Large Tongue Orchid or Cow Orchid. This tall (40 to 110 cms) evergreen orchid is common in the eastern states where it is commonly found in damp areas as well as swamps. but in South Australia it is limited to swamps and is rated as endangered.

Leo Davis makes some interesting observations about the structure of this flower in his article Upside Upside Down which is well worth reading (https://nossa.org.au/2017/03/03/upside-upsisdedown/).

Whilst not an easy orchid to grow it has been cultivated although seed set has not always occurred. Helen Richards, an experienced Victorian terrestrial orchid grower, shared in an email how she grows them.

Cryptostylis species grow from brittle rhizomes which can be quite long and they resent frequent disturbance. Mine are potted into a pot therefore that is large enough for the long roots and which will accommodate further growth for several years. My mix is ANOS basic mix, the same as I use for Pterostylis and many other genera. They need to be kept moist all year round, especially in summer when they flower and new leaves appear, their active growing period. I grow them in an area of moderate light. Others have seen pollinators active on the flowers but I haven’t. However seed capsules frequently develop without my assistance with a toothpick. Richard Thomson says they haven’t had success germinating the seed.”

Reference

https://nossa.org.au/2017/03/03/upside-upsisdedown/

http://bie.ala.org.au/species/http://id.biodiversity.org.au/name/apni/89052

http://saseedbank.com.au/species_information.php?rid=1288

Personal communications Helen Richards (OAM), Chairman Australian Orchid Foundation

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

The other entries :

1702 sm RWL Spiranthes alticola

1702 sm RAL Pterostylis falcata

1702 sm PM Thelymitra villosa

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.

Mad Dogs and …. Orchidologists

Mad dogs and Englishmen are not the only ones to go out in the  midday sun.  For orchidologists to see Sun Orchids flowering, then it is out into the midday sun on a hot day because that is when they open.  There is no point going much before 11am and by 2pm most are closing and no point going out on a cool or windy day.

1604 sm CC T benthamaniana

But for those who don’t want to  go out (or cannot get out) into the midday sun, here is a video to be viewed in the cool of the shade.

This video features the Leopard Sun Orchid (Thelymitra benthamiana) an uncommon Sun Orchid in South Australia.  Unlike many sun orchids which requires a view of the flower to confirm identification, this one can be identified by the leaf alone.  At the beginning of the video take note of its distinctive leaf.

Thelymitra benthamiana

September 2016 Winning Picture

Spring is here and it was reflected in the variety and large number of entries.  Lorraine Badger and Ros Miller entered Western Australian species – Caladenia x ericksoniae (Prisoner Orchid) and Paracaelana nigrita (Flying Duck Orchid) respectively.  The other six entries were all from South Australia, Diplodium robustum (Common Green Shell Orchid), Caleana major (Flying Duck Orchid) both from Jane Higgs, Greg Sara’s Oligochaetochilus sp (Rufoushood), Judy Sara’s Arachnorchis leptochila (Queen Spider Orchid), Claire Chesson’s Diuris behrii (Cowslip Orchid or Golden Moths) and the outstanding winning picture Pterostylis cucullata by Bevin Scholz.

 1609-sm-bs-pterostylis-cucullata

In many ways, Bevin’s picture of P. cucullata (Leafy Greenhood) is a special picture because it represents some of the conservation work with which NOSSA is involved. For many years NOSSA has worked with the Threatened Plant Action Group (TPAG) to weed the areas in Belair where this species is located and to see such a good show of plants is encouraging.  It is a tribute to all who have contributed with their time and labour.

P. cucullata is rated Vulnerable both in South Australia and Victoria, and Endangered in Tasmania. It is also rated Vulnerable under the EPBC Act (Federal). Nationally it is known from about 110 sites with most of these sites being in Victoria and only a few sites in South Australia with Belair National Park having the largest and most important population for the state.

Historically this species covered an area of 2107 km2 in the Lofty Block region but that has now contracted by 82% to only 366 km2 with few locations. With such a reduced range, recovery plans were developed, both at state and federal level.  The plans examined the risks and threats to the survival of the different populations.

One of the threats to this orchid is fire, including proscribed burns.  Unlike some species such as Pyrorchis nigricans, Leptoceras menziesii or Prasophyllum elatum which flower well after fire, P. cucullata is fire sensitive; populations decline substantially.  There does not seem to be a safe time to burn for this species.  Should a population survive a burn, it would take it many years to recover.

Fire also leaves the population vulnerable to another threat, that of weed invasion.  Unfortunately, it is weedy where this species survives but over the years, a consistent, targeted weeding program has resulted in a declining weed population.  NOSSA and TPAG have appreciated the work and effort of volunteers and gladly welcome anyone else who would like to join. And one of the rewards? A beautiful, sunlit display of flowers as seen in Bevin’s picture.

Reference:

Duncan, M. (2010). National Recovery Plan for the Leafy Greenhood Pterostylis cucullata. Department of Sustainability and Environment, Victoria https://www.environment.gov.au/system/files/resources/14e1ae30-5cf7-4be6-8a35-2c752886c14f/files/pterostylis-cucullata.pdf

Nature Conservation Society of South Australia (2009) DRAFT RESPONSE ON THE BELAIR NATIONAL PARK TRAILS MASTERPLAN: PRELIMINARY ISSUE January 2009  http://www.ncssa.asn.au/images/stories/ncssasubmission_belairnptrails_masterplan_jan09_final.pdf

Quarmby, J.P. (2010) Recovery Plan for Twelve Threatened Orchids in the Lofty Block Region of South Australia 2010. Department of Environment and Natural Resources, South Australia https://www.environment.gov.au/system/files/resources/e362cfd2-a37b-443a-b007-db3a2b7b64dd/files/lofty-block-orchids-recovery-plan.pdf

CULTURE NOTES FOR EPIPHYTIC ORCHIDS in ADELAIDE 2016

Dendrobium speciosum

Epiphytic orchids grow on trees or rocks (lithophytic), where they are dependent on their host for support but not for food.

CULTIVATION

The majority of Australian epiphytic orchids can be easily grown in cultivation.  Most can be grown in Adelaide if the correct cultural requirements are provided.  These include controlled glasshouse conditions, shadehouse conditions and, in some instances, in the garden.  Only a few species are able to tolerate the cold winter months in Adelaide without extra protection, and all need protection from frost.

CONTAINERS AND MOUNTS

Plants can be grown in pots or mounted on an appropriate substrate. Pots may be either plastic or terracotta.  Terracotta pots are porous and dry out more quickly than plastic.  If terracotta pots are used, their drainage holes may need to be enlarged to give very good drainage.  Plants should be potted into the smallest pot, which comfortably accommodates the base of the plant.

Plants may be mounted on materials such as compressed or natural cork slabs, branches of rough barked trees, black weathered tree fern slabs and pieces of weathered hardwood.  Brown tree fern slabs contain substances, which are toxic to orchid roots and are not suitable.  Those species that have a pendulous habit e.g. Dendrobium teretifolium should only be mounted.

POTTING MIX

Most potted orchids require a mixture made up of bark chips (fir or pine), to which may be added charcoal, gravel or polystyrene chips, in which to grow.  Bark used should be aged and preferably purchased as graded hammer-milled bark, not shredded bark.  Fresh pine bark contains compounds, which are toxic to orchids.  Before use fresh pine bark should be soaked in water changed regularly, to remove toxins.  This may take 3 weeks.  If in doubt as to the freshness of the bark, treat as above to be sure.

Depending on the size of your plant, bark may vary from 5-7mm up to 20mm in diameter, and sieved if necessary to remove fine particles and dust.  Other substances such as scoria, leaf mould and coarse grit may also be added according to the requirements of the particular species involved.  Whatever the substrate, be it a slab or potting mix, the essential thing with all epiphytic orchids is to always provide good drainage for the plant’s root system.  This ensures no, or minimal, root rot of plants.

Repotting is necessary when the potting mix breaks down resulting in poor drainage, the medium goes stale or when the plant over grows its container.  The best time to repot is during the spring, after flowering, when the plant starts to actively grow again.  Try to repot every 2-3 years.

Potting on:  If the plant has overgrown its container and the mix has not deteriorated, it can be potted on into the next sized pot with minimal disturbance to the root system.

D kingianum composite (2)

GROWING ENVIRONS, HOUSING

Garden Culture

Several species may be grown outside in Adelaide, provided they are given a position sheltered from frosts and hot drying winds.  They should receive daily supplementary watering during the summer.  They may be tied on to trees with rough non-deciduous bark or grown on rocks.  Microclimates can be created in areas of the garden using screens for protection and other plants to help maintain a humid atmosphere.

Bush house, Shadehouse

These structures are built to give protection from frosts, strong winds and sun and to provide extra humidity for plants.  They may be covered with shadecloth or tea-tree and should have a solid south wall.  They provide protection, but still allow for good air circulation around the plants.  A water impervious roof, e.g. fibreglass or polycarbonate sheets, will protect plants and flowers from excess water in the winter.


Unheated glasshouse

An unheated glasshouse gives more protection to the plants, achieving higher temperatures during winter days, and better humidity.  It may be made from glass or other materials such as fibreglass or polycarbonate sheets.  Additional shading with shadecloth or paint is necessary from October to March-April.  Adequate ventilation must be provided, by using ventilators under the benches to let in fresh air, and roof ventilators to let out hot air.  Alternatively, air circulation can be achieved using fans.  All orchids love fresh air.

WATERING

All plants need to be watered frequently from October to April, during the growing period.  Most species require watering once a day or twice a day if the weather is particularly hot or drying.  Ensure that plants dry out between waterings.  During winter, watering once a week should be sufficient for plants in a glass house environment, although plants which are mounted may be misted (a very fine spray) more frequently.  Water early in the morning of winter days to ensure that the leaves of the plants have dried off by night.  Water lodging in leaf axils in cold, comparatively still conditions, renders that area liable to fungal attack.  Humidity may be maintained by watering the floor and under the benches, particularly in summer.

Rainwater, if available, is preferable to mains water, which can. In some cases, increase in salinity to a level, which is harmful to good plant growth.

FERTILISING

To promote healthy growth of all epiphytic orchids, a supplement of half strength liquid fertiliser every two weeks may be used during the growing season of the plant, i.e. November to April.  Mature potted plants can be sparingly fertilised with slow release pellets.  Too much fertiliser will lead to a salt build up (especially in charcoal), which will harm the plants.

PESTS

Pests will become a problem in any shadehouse or glasshouse if the grower does not keep a watchful eye out for them.  The shadehouse or glasshouse should be kept free from weeds, decaying organic matter and rubbish, as these are the places where pests feed and accumulate.  Overcrowding of plants will also encourage pests to thrive.

Pests can be easily removed by squashing if they are in small enough numbers.  A pest strip hung in the glasshouse successfully controls many pests. Unfortunately the environment of a glasshouse, which suits orchid culture, also provides a suitable environment for the spread of pests.  Poisonous chemical sprays should only be used after non-toxic preparations have been unsuccessfully used.  These chemicals also destroy the natural predators of insect pests, upsetting the natural balance.

Caution should be used when handling chemical sprays as many are very toxic to the user as well as the pests.  The manufacturer’s directions and warning labels should be read carefully and recommended strength adhered to strictly.

DISEASES

Australian epiphytic orchids are generally disease free.  Fungal infections may occur, susceptible areas being new growths, especially in young plants.  These can be kept to a minimum by maintaining good air movement and avoiding water remaining in leaf axils for too long.  Broad spectrum fungicides are suitable to control severe infections.

PLANT CARE

Removal of any dead leaves, pseudobulbs, etc, not only enhances the aesthetics of the plants, but also lessens the chance of further deterioration.  These areas are also the places where pests may accumulate or diseases harbour.

Dendrobium bigibbum

Dendrobium bigibbum