When do I stop watering my Greenhoods?

This was the question posed to Les Nesbitt at the September monthly meeting.  Later there was some further discussion, of which see below:

When do I stop watering my Greenhoods?

The short answer is when the leaves go yellow and start to die off, usually in October- November. Allow the pot to dry out completely to dry up the roots and old tubers so that they do not go mouldy and rot the new tubers.

Australian terrestrial orchids form tubers underground. The mature plant dies back at the end of the growing season and enters a period of dormancy which for South Australian terrestrials is over summer.

A general principle of watering is to match the watering to the rainfall pattern. Whilst there is minimal rain over summer, when dormant tubers are in pots it is important to not let them stay dry for months and become desiccated. A light sprinkling every week or two is sufficient.

Unicode

Pterostylis ‘Nodding Grace’ This is an hybrid between P. nutans and P. curta. Obviously it is not time to stop watering.

When do I start watering again? 

For the cauline group (Diplodiums) from South-eastern Australia start watering at the end of January as the tubers are starting to shoot by then. For other greenhoods start light watering in late February and gradually increase the water until shoots appear usually in March-April. Do not let the pots dry out once leaves are visible.

Diplodium robustum - one of the cauline greenhoods

Diplodium robustum – one of the cauline greenhoods. Note difference the between the leaves of the non-flowering rosettes and the flowering plants.

Other cultivated Australian terrestrial orchids require a similar watering regime although leaves of some appear later in May or June.

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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

References

Websites accessed 1 July 2015

White Beauty Spider Orchid (Caladenia argocalla) Recovery Plan
http://www.environment.gov.au/archive/biodiversity/threatened/publications/recovery/c-argocalla/index.html
Caladenia argocalla – White-beauty spider-orchid, biodiversity species Profile and Threats Database
http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=54991
Recovery Plan For twelve threatened Orchids in the Lofty Block Region of South Australia
http://www.environment.gov.au/system/files/resources/e362cfd2-a37b-443a-b007-db3a2b7b64dd/files/lofty-block-orchids-recovery-plan.pdf

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

The Great Orchid Pretender

Actually there is more than one.

Frequently NOSSA receives a request to identify an orchid in someone’s garden.  Often, instead of an orchid (but occasionally there are orchids), it is the Ariasrum vulgare (common name Friar’s Cowl Lily or Cobra Lily).

Native to Asia and Europe, notably the Mediterranean and introduced to Australia, it is often mistaken for one of the flowers of the Pterostylis (Greenhood Orchids) or Diplodium (Shell Orchids).  Some have called it a Blackhood orchid others Snake Orchid.  It’s resemblance to the Greenhoods and Shell Orchids is superficial as they have none of the orchid features.  The dark purple hooded part is not the flower; it is a spathe (bract).  The flowers are minute hidden on deep down on the “tongue”.

The hood of the orchids is the combination of a deeply concave dorsal sepal interlocking with the lateral petals; and the fusing of the two lateral sepals.  Tucked away within the hood is the labellum (a modified petal) and the column (the reproductive organs of the flower).  The leaves of Ariasrum are quite large and distinctly different from any of the Greenhood orchids.

Friar's Cowl Lily 93RL

Arisarum vulgare amidst its large leaves

Pterostylis pedunculata 92RL

Pterostylis pedunculata (Maroonhood Orchid)

Diplodium robustum 92RL

Back view of a Diplodium robustum showing the dorsal sepal and two lateral petals that make up the hood of the flower

 

 

 

 

 

 

 

 

 

Diplodium robustum labellum and column 96HL

Looking into the Diplodium robustum – the labellum is the brown tip just visible at the front of the flower and the column is the brown white and yellow structure at the back

Pterostylis curta Labellum and column 92RL

Peering into the hood of a Pterostylis curta, the labellum is toward the front and the white and yellow structure to the back is the column

Friar's Cowl Lily open bract 93RL

The bract of the Arisarum vulgare has been split open to reveal the knobs which are the flowers. The flowers are so small a hand lens or microscope is needed to see them.