CULTURE OF FAST MULTIPLYING (FM) TERRESTRIAL ORCHIDS

Recently, NOSSA updated the Terrestrial Culture Fact Sheet.  Instead of one sheet, it was decided to split it into three – Culture of Fast Multiplying Terrestrials, Culture of Slow Multiplying Terrestrials and Culture of Fungi Dependent Terrestrials.  Though much of the growing information is similar, there are some significant differences of which growers need to be aware.  The first of the fact sheets is Culture of Fast Multiplying Terrestrials.

FLAGBEARER SPECIES: Pterostylis curta

Pterostylis curta Labellum and column 92RL
Pterostylis curta (Blunt Greenhood) is rated rare in South Australia.  Ex situ conservation is another dimension to conservation.

Others include Chilogolottis, Corybas, Cyrtostylis, Diplodium, Microtis most Pterostylis and some Diuris. Most FMs are Autumn or Winter flowering. The exceptions are Diuris and Microtis. FM are the most common terrestrial orchids to be seen at meetings and shows. Once seedlings are established they are no longer fungi dependent.

GROWTH HABIT: FMs are the easiest terrestrial’s orchids to grow. They multiply by forming 2 – 5 tubers per plant each year. The annual growth cycle comprises 6 – 8 months as growing plants under cool (5 – 20⁰ C max, 0 – 14⁰ C min) moist conditions and 4 – 6 months as dormant tubers in hot (18 – 42⁰ C max, 12 – 30⁰ C min) dry conditions.  New tubers are produced in winter/spring. FMs are colony types, ie they multiply annually and will spread out over time if planted in the ground. 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. FMs mainly flower in Autumn and Winter. Diplodium & Pterostylis leaves are usually the first to appear in March followed by Diuris and Microtis in April, and Corybas in June to July. In October/November the leaves go yellow, 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. Sun loving species (Diuris & Microtis) prefer a brighter location for good growth. Corybas like the shadiest corner.  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 amount of light should be increased.

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.

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 matt 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: They grow better if repotted annually otherwise the plants crowd together around the rim of the pot.  Repotting is normally done between November and January. The pots can be knocked out and the tubers examined without harm.  For best results repot the tubers in half fresh soil mix. A suitable soil mix is 40% loam, 50% sand and 10% organic matter with a little blood and bone fertilizer added. (They will also grow in native potting mix.) A 5 mm sieve is a useful tool for separating tubers from soil. Replant the dormant tubers with the tops 20 mm deep. Cover the soil surface with a mulch of chopped sheoak needles (20 – 50 mm lengths). This prevents soil erosion and assists with aeration under the leaves.

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 mite and fungal diseases in the warm weather.

FERTILIZING: FMs are very hardy and will benefit from weak applications of folia feed in the early growth stages.

OTHER CULTURE NOTES:

NB: IT IS ILLEGAL TO TAKE PLANTS (WHOLE PLANT, FLOWERS, SEEDS AND TUBERS) FROM THE WILD

 

Moving Labellums

The following article titled Moving Lablellums written by Helen Lawrence is reproduced from the NOSSA Journal Volume 36 (1) February 2012

Labellums are fascinating. Well I think they are fascinating, especially the ones that move.

Bunochilus viriosus labellum down
Bunochilus viriosus with the labellum down

Why do these labellum move? You may have observed that the orchids which have labellums often have “hoods” and inside these “hoods” are the pollen. It is quite simple, the pollinator lands on the labellum, triggers it and is held captive by the labellum. As it struggles to free itself it pollinates the orchid. Clever, isn’t it?

Bunochilus viriosus labellum up
Bunochilus viriosus with the labellum up

So that these labellums can capture the insect they need to be sensitive. Consequently they can easily be “set off.” This can happen with of a gust of wind, or if the plant is in a pot, the labellum may trigger if the plant is moved/knocked.

It is easy to see these labellums as they move up into their “triggered position.” They move reasonably quickly, so the insect does not have time to respond.

However, how does the labellum return to its “normal” position? Does it slowly return to the position, or does it happen in a sudden movement in the same manner as when it is triggered?

One day when I was travelling in the car with a Pterostylis curta (Blunt Greenhood), I observed something very interesting. When I looked at the flower, the labellum was up, but then when I looked at it a minute or two later, the labellum was down. The labellum had to move quickly. However was it the bumps in the road which caused it to move? I had to find out.

I devised an experiment to satisfy my curiosity, and find out what these fascinating labellums actually do.

First I had to find an orchid with a labellum that could be triggered. I ended up using an Oligochaetochhilus bisetus (Two-bristle Greenhood).

Oligochaetochilus arenicola
Oligochaetochilus arenicola

Second I had found a good camera that could take high definition video. I placed it on a “tripod” (a pile of books).

So I had set up my apparatus, set the camera rolling, triggered the labellum, and left the room.

So what happened?

For the first six minutes after I had triggered the flowers nothing happened. There was no movement that I could see.

In the next five minutes, the labellums of the two flowers slowly moved downwards until they were half way down.

After twelve minutes of the flower being triggered, the labellum returned rapidly to its original position. This final stage of the labellum moving lasted for less than five seconds, and appeared to move at the same speed as when it was triggered.

So it looks like the labellum returns to it normal position first moving slowly and then in a rapid final movement which returns the labellum to its original position.

Urochilus sanguineus
Urochilus sanguineus

If I thought it would be that simple, I was mistaken.

As I briefly looked through the fifty minute video I took, I came upon something that made no sense to me.

A minute after the labellum had returned to its resting position, one of the labellums suddenly returned to its “triggered” position. What’s more, there was nothing in the room to trigger the labellum: no wind, no insects, and no people. So what triggered the flower?

I do not know. Six minutes after the labellum was triggered it returned to its original position, and then two minutes later the other flower’s labellum moved into the triggered position. The first flower was triggered again for no apparent reason at all, four minutes after the second flower was triggered and still remained up.

Once the labellums returned to their original position, there was no more movement.

Maybe triggering the labellum causes a chain reaction. Maybe the labellums periodically “trigger themselves.” Well, I can’t give you any answers, all I can tell you is that it looks like this is an example of how we barely know anything about these wild gems. They are beautiful but bizarre and of course fascinating!

After 7 minutes, just before the labellum moved
After 7 minutes, just before the labellum moved
After 12 minutes, labellum about to fall
After 12 minutes, labellum about to fall
After 13 minutes, labellum in original position
After 13 minutes, labellum in original position

 

 

 

 

 

 

 

 

 

 

 

As a 50 minute video is a bit long to watch, Helen has produced a four minute video, so watch and enjoy the music!

2014 November Photograph Competition Part 2

Part Two of the November competition consisted of photographs of insects on orchids. There was quite a range of insects but the winner was a draw between Cyrtostylis robusta (Winter Gnat Orchid) with an ant and Pterostylis curta (Blunt Greenhood) with a midge fly; both taken by Doug Castle.

With today’s technology it is not only easier to take crisp images but fine details can be seen particularly when enlarging the image. Hence when the pictures are enlarged it is possible to see hairs on the ant and feathered antennae on the midge fly.

With identifying orchids, it is often the detail that is important. Both of these orchids are distinctive and can be readily identified but it is good to examine why this is the case.

Pterostylis curta (Blunt Greenhood)
Pterostylis curta (Blunt Greenhood)

With the greenhood, there is enough detail to see that the dorsal sepal and lateral petals have united to form a galea, ie hood, and that the lateral sepals are semi-fused and erect resulting in lateral orifices (side gap) between the two structures. These are some of the features that separate Pterostylis* from the other greenhoods such as Diplodium, Speculantha and Taurantha. This becomes apparent when browsing through the greenhood photographs, pages 286 to 339, in Jones “A Complete Guide to Native Orchids of Australia”. Having established that the plant is a Pterostylis, the twisted labellum is diagnostic of a P. curta as it is the only one that is described with a twisted labellum. Although not all the identifying features are present, enough information is available in this picture for identification.

In contrast the photograph of the Cyrtostylis robusta only has sufficient data to confidently identify it as a Cyrtostylis species, having a distinctive labellum that is larger than the lateral sepals and petals. In South Australia there are only two species and according to Bates (2011), the distinguishing features between the two

Cyrtostylis robusta (Winter Gnat Orchid)
Cyrtostylis robusta (Winter Gnat Orchid)

appear to be the leaf, the bud and the labellum. In this picture, the angle of the image does not give a clear view of the labellum (it could possibly be damaged) and of course there is no bud or leaf. It is possible that the pale edges of the dorsal sepal may give a clue to species identification as C. reniformis has mainly darker buds than C. robusta. Obviously Doug was able to identify it from his observations of the other features not present in this photograph.

In summary, one image is not always sufficient for identification. As was discussed on the night, to confirm identification, orchids should always be photographed from more than one angle, including pictures of other parts of the plant.

*In South Australia, Pterostylis foliata is a possible exception as it has no obvious lateral orifice.

References

Jones, D.L., T. Hopley, S.M. Duffy, K.J. Richards, M.A. Clements & X. Zhang (2006) Australian orchid genera. An information and identification system. CSIRO Publishing: Collingwood, Vic.

Bates, R.J. (2011) South Australia’s Native Orchids. DVD-ROM. Native Orchid Society of South Australia Inc.: Adelaide.

Jones, D.L. (2006) A complete guide to native orchids of Australia, including the island territories. New Holland Publishers: Sydney.