Again this month was a varied selection of species with Pauline Myers’ Caladenia chapmanii (WA), Claire Chesson’s Thelymitra rubra, Jenny Pauley’s hybrid of Arachnorchis brumalis x conferta, David Hirst’s Caladenia discoidea and the winning entry, Rosalie Lawrence’s Diuris brevifolia.
This strikingly yellow flowered donkey orchid endemic to South Australia is listed as Endangered. Its range was once quite widespread in the southern Adelaide Mt Lofty Range region but now it is now restricted to pockets on the Fleurieu Peninsula and western Kangaroo Island in Heathy Woodland, Wetland and Riparian habitats.
There is interest today in cultivating orchids for conservation or ex situ conservation. With the reduced range of this species, can it be cultivated and thus continue to ensure its survival as a species? Some sources seem to suggest that it is an easy plant to cultivate, and some Diuris are easier than others, but Les Nesbitt points out that he has some plants from a rescue dig several years ago and that they have not multiplied very much in that time. This suggests that they may be dependent on a specific fungi. Though it has not been hugely successful in cultivation, it is worth noting that it has been used to produce hybrids with several other Diuris.
Bates, R. J. (2011) South Australia’s Native Orchids NOSSA DVD, Adelaide
Nesbitt, L personal communications
Adelaide and Mount Lofty Ranges South Australia Threatened Species Profile Fact Sheet – Diuris brevifolia
Here in South Australia, it is very common to see a covering of She Oak needles (Allocasuarina sp.) on pots of terrestrial orchids. According to Les Nesbitt, NOSSA founding member and experienced terrestrial orchid grower, there are four reasons for this
It keeps the leaves up off the soil.
Provides good air circulation
Helps prevent leaf rot.
It provides nutrients to the fungi
This is very important for the fungi dependent orchids.
It stops pitting into the soil when it rains.
This is most likely to occur when pots are under the drip line of a shade-cloth.
Pitting exposes the root system.
It allows the leaves to readily come through because of its small diameters.
Other mulches, such as gum leaves, smother seedlings.
She Oak needles are the choice of mulch because it is
Long lasting and takes more than year to break down
which means that it lasts the whole growing season.
Does not become mushy or spongy
unlike pine needles and grass cuttings which breakdown more quickly into a wet soggy mass and contribute to leaf rot.
It should be noted that it is necessary to replace this mulch yearly.
In 1984, G.J.Nieuwenhoven was the editor of the NOSSA Journal. In February of that year he wrote the following:
Welcome back to NOSSA.
After the holiday break we are all looking forward to the next meeting to talk about our favourite plants and renew friendships.
Several members have reported an early start to the terrestrial season with Pterostylis species, a couple of Diuris species popping up already. For some of the eastern states Pterostylis of the cauline group this is normal, especially if you keep the pots cool during the summer (a cellar is ideal but underneath a shaded bench in the shadehouse will do nicely). Very light watering should take place when the first shoots appear but do not overdo the watering or place pots in the sun for we are sure to get some more hot weather yet and this could cook your plants before you know it.
The Diuris are really out of season but it was probably the rain in late December and early January that started them off, anyway, these too should be kept slightly damp if they are up.
If you have not finished repotting by now it would be best to leave it until next year as the new shoots which are already beginning to grow from the tubers are very easily broken off while sifting them from the soil.
Apart from that all you can do is wait for the rains to come in March and then start searching for plants to appear – and keep those fingers out of the pots or you may damage one of your best plants looking for the new growths.
This is also the time to start taking notes when plants first appear, etc.:
when they flower and how many flowers from a given number of tubers;
what kind of soil; what conditions (i.e. shaded or not, damp or dry).
Anything that may assist in years to come to help you understand and grow our orchids better and, more importantly, multiply them.
A card index system would be a good way to store information, otherwise an exercise book will do.
The timing of the article tallies with the advice that was recently given at the end of February – start watering the terrestrials now if you haven’t already begun. Hopefully by the flowering time you will have a lovely display of terrestrials such as the Thelymitra, Arachnorchis and Caladenia featured below.
Back in 2013, Gardening Australia of the ABC produced a video featuring Helen Richards, a Victorian who has in-depth knowledge of growing terrestrial orchids. Though Helen lives interstate and adaptions do need to be made for different locations and conditions, this video of her shadehouse is very instructive for any South Australian’s wanting to grow their own terrestrials.
This month’s entries of Oligochaetochilus arenicola, Caladenia flava, Calochilus robertsonii , Diuris palustris and Caladenia procera illustrated the variety of shapes to be found in orchids.
All but one are reasonably common; all but one were photographed in situ and that one was the winning picture by Kris Kopicki – Caladenia procera. Its common name, Carbunup King Spider Orchid, reflects its location near Busselton Western Australia. This species has a severely limited distribution with a small population and is threatened by land clearing for development. Consequently it is rated as critically endangered.
The other aspect of this plant is that it is a photograph of a plant in a pot not the bush. Kris benched the original plant at the September Tuesday meeting when it was still in bud. By Saturday it was in glorious flower.
This picture exemplifies the two objects of NOSSA which “are to promote and engage in activities for the promotion and furtherance of:
the culture, propagation, conservation, knowledge and scientific study of the native orchids of Southern Australia and the Australasian region;
the preservation of orchids as a species and their preservation within their native habitat.”
Some terrestrial orchids are relatively easy to grow but not this one. It takes time patience and skill to grow them. C procera is one of the fungi dependent species and though capable of living many years, it can take up to six years before flowering, although under ideal condition it could mature in as little as two years.
Being able to grow the different terrestrial orchids is one of the ways NOSSA can help in their conservation. NOSSA has a Growers’ Forum each meeting night where members can attend and learn from experienced growers how to grow both epiphytes and, importantly, the terrestrials.
Native Orchid Society of South Australia Inc. (NOSSA) Rules of Association 2007
Some native terrestrial orchids only flower in the season after a bushfire. They are stimulated by the hot gases given off during the fire. One of those gases is ethylene. Bananas are shipped down from Queensland to the southern states of Australia as green bananas to stop fruit fly outbreaks. On arrival they are put in sealed rooms and exposed to ethylene gas. The bananas ripen a few days later. Traces of ethylene remain in the banana skin. Overripe fruit also emits ethylene gas. Orchid flowers do not last long if ethylene is present in a closed glasshouse.
We know that dormant tubers exposed to ethylene often flower the next season. The best example is the Hare orchid Leptoceras menziesii. In summer I put dormant tubers in a small dish in a plastic bag with a banana skin and seal the bag with a rubber band. The skin may go mouldy so should not touch the tubers. I leave the bag inside my shed for about 2 weeks then remove the tubers and pot them up. The exposed plants make leaves almost twice as large as normal tuber leaves. This procedure should not be carried out with the same plants the following year as they may get exhausted and die out. I have found results with other shy flowering species are not so reliable. Maybe they need a stronger does of ethylene.
Ever since the Western world discovered the orchid in the 18th and 19th century there have been enthusiasts wanting to grow them but though an orchid may produce millions of seeds, for they are minuscule, only a relatively small number germinate. The seeds do not have any stored food and are dependent upon fungi for germination. This made it difficult for early orchid growers who relied on obtaining specimens from the wild – a most unsustainable practice!
Yet today cultivation of orchids is flourishing. It is not dependent upon removing specimens from the bush. In Australia it is illegal.
Today the orchid enthusiast can grow orchids from seeds at home. The technique, invitro embryo germination, is popularly known as flasking. It involves growing the seeds in a sterile agar medium to which the most significant ingredient was the addition of sugar.
At the time it was developed by Professor Lewis Knudson (1884 – 1958) of Cornell University in 1922 this method was revolutionary.
Rasmussen J, April – June 1986, “Contact Dermatitis from Orchids” Clinics in Dermatology Volume 4 Number 2
Below are some examples of terrestrial orchids grown from seeds in flasks.
Replanting in bushland should be restricted to orchid species that grow or once grew in the local area. Nohybrids please.
If planting out in the garden or bush, choose a location with good air movement and winter sun and a thin layer of surface mulch. Slashed native ground cover is good. Native terrestrial orchids cannot stand competition from weeds, grasses, slugs and snails and scratching blackbirds (all introduced pests). They will rot away in dense weeds or dense understory plants. If in a frost prone area they may need overhead protection from a shrub or trees. For plants in growth, dig out a hole a little bigger than the tube. Knock out the tube and insert the contents into the hole and backfill with as little disturbance as possible. Dormant tubers can be planted in a furrow, 50mm or more deep, and backfilled just like planting beans. Water in. The colony forming species will spread out and form patches of plants over a period of several years.
Orchid seed is like fine dust and can be mixed with fine dry sand to help spread it over a large area. Broadcast using a pepper-shaker over a suitable site. Results are dependent on the season and whether fungi are present. This method is slow to show results as flowers may not be seen for 5 to 10 years after seed is sown. More seedlings germinate if there are mother plants already growing.
A pot of Arachnorchis argocalla, 40 cm tall (Fungi Dependent)
To learn more about re-establishing orchids in the bush, visit the Vale Park Our Patch website to see the work being done by Heather Whiting and her team.
During summer, very lightly water surface of pots weekly to prevent tuber desiccation especially if dormant seedlings are in the pot.
Divide overcrowded pots in summer. Tip out and break into slices like cutting a cake. Stand a slice in a new pot & fill spaces with fresh mix. Take care to keep the surface layer at the surface of the new pot.
Add fresh leaf litter to surface layer in January to February to March.
If surface moss gets too thick, peel it off and discard in summer.
Start heavier watering of pots weekly from mid March.
Mix seed with fine dry sand and sprinkle on mother pots in April.
Water as required in autumn, winter & spring so that pots never dry out during the growing season yet are not soggy wet.
Leaves appear from Anzac Day to June.
Look for flower buds down inside the largest leaves from mid July onwards.
Look for new seedling leaves from August to October.
Enjoy and photograph flowers September to November.
Hand-pollinate flowers in September – October. Flowers collapse within days of fertilisation.
Collect seed pods as they turn brown just before they split open in November – December.
Dry & store seed over summer in paper envelopes kept indoors.
Allow pots to slowly dry out in mid – late November to induce dormancy and ripen tubers. Plants die down completely in summer to underground tubers.
For further information on growing fungus – dependent orchids refer to:
‘Orchids Australia’ February 2006, P58, or ‘The Orchadian’ Vol 15, Number 3, March 2006, P100.
Caladenia latifolia cultivated by LN (Fast Multipler)
Terrestrial orchids can be placed into one of three groups that have similar cultural requirements.
Fast multipliers with an annual increase rate greater than 1.5
Slow multipliers with an annual increase rate less than 1.5
Fungus dependent orchids survival rate less than 1
Fast multipliers (FM):
Fast multipliers are the easiest deciduous terrestrials to grow and potfuls are regularly seen at orchid meetings and shows. They multiply rapidly by forming 2 – 4 tubers per plant each year. They will take some fertiliser and grow better if repotted annually. It is usually not commercially viable to grow seed of these in flask. They will grow well in premium potting mix from your local hardware store with some sand added. This group contains many genera including Acianthus, Chiloglottis, Corybas, Cyrtostylis, Diplodium, Leptoceras, Microtis, Pterostylis and some species from Caladenia, Diuris and Thelymitra.
Slow multipliers (SM):
Slow multipliers are not so easy because there is less room for error. Some very showy Diuris, Pterostylis and Thelymitra fall within this group. A few have a near zero increase rate and will fade away unless additional plants can be produced to make up for occasional losses from predators and disease. They are more expensive because they have to be raised from seed in flasks. Flowering plants are hand pollinated and the seed collected just before the pods split open and the dust-like seed blows away. The pull-off-the-tuber method can be used with some Diuris and Pterostylis species to double plant numbers annually. Do not fertilise these except when repotting. Those with large tubers such as Thelymitra nuda and Diuris behrii should be the first to be repotted in November – December.
Fungus dependent orchids (FD):
Some of Australia’s most fascinating orchids rely on a symbiotic fungal association to obtain nutrients from the soil as these orchids have virtually no roots. The majority of Australia’s terrestrial orchids are in this group and many are rare plants as they seldom multiply. We talk about survival rates for these orchids that are normally less than one. Propagation is from seed. They have a reputation for being difficult to grow in pots. However some species have been kept alive in pots for nearly 30 years. Never use fertiliser because it can kill the fungi. They should be repotted only when the tubers reach or come out of the bottom of the pot or seedlings get too crowded. A new thin layer of leaf litter is added to the surface each summer to feed the fungi which is active near the surface. Flowers are hand pollinated to get seed. Seed is sprinkled on the pots each autumn and with good culture, seedlings will appear in spring around mother plants.
Since the fungus cannot be seen with the naked eye, the health of the leaves is used to indicate that the fungal relationship with the orchid is working. If seed is sown in autumn, by springtime, when mature orchids flower, there may be a new crop of tiny seedling leaves around the base of the large mother plants. The appearance of new seedling leaves around mother plants each spring confirms that the fungal relationship is healthy. Seedlings take 3 – 5 years to reach flowering size.