Monthly Terrestrial Orchid Culture – May

The following article by Les Nesbitt is taken from the Native Orchid Society of South Australia Journal, May 2019, Volume 43 No 4. The article has been slightly modified with editorial changes in black.

The majority of terrestrials will have leaves showing by month’s end. A few stragglers like South Australian Corybas and Western Australian Cyrtostylis huegelii will not appear until June so do not panic yet.

Pterostylis truncata (little dumpy) flowers this month with a large flower on a short stem. This species is given a blue tag to denote watering from January otherwise there will be no flowers under Adelaide conditions.

Tasks for May

  • Move the Autumn flowering greenhoods under cover as the flowers open because they generally have tall thin stems that will bend over under the weight of rain drops on the flowers.
  • Rot can be a serious problem in May. Do not overwater if there is little rain; and inspect plants closely and often. The rot can be on the leaves or below ground. Look for plants that are not thriving and give them a gentle tug to see if there are any
  • Move infected plants away from healthy plants to a hospital area under cover. Water from below by standing the pot in a saucer of water. Keep the leaves dry. Good air movement and at least 5 hours sunlight a day are essential for the next 3 months.
  • The fast multiplying orchids will appreciate a weak dose of liquid fertilizer once a month until spring.
  • Weeding is a chore this month as weed seeds germinate after rain. Pull them out while they are small maybe even with the help of tweezers.

Virus

Inspect plants closely for virus as the symptoms show in the emerging leaves. All plants can be infected with viruses of which there are many. There is no cure for virus. Infected plants must be destroyed to prevent virus spreading to healthy plants via sap sucking insects or human activities spreading sap. Infection during the growing season does not show up in the leaves until the following year. It is difficult to eliminate virus entirely hence the need to be vigilant.

Signs of Infection

  • Virused Pterostylis leaves may have light & dark green blotches or be thicker than normal and look crippled or turned up at the edges.
  • Another sign to look for are pointed pimples on Caladenia and Pterostylis
  • Virus is harder to spot on the narrow leaves of Diuris and Thelymitra. Healthy leaves are straight with almost parallel sides. Leaves that have kinks or are curved probably have a virus. Variegated blotching may be present in severe cases.

Managing

  • If only one or two plants, in a community-pot, show symptoms they can be lifted out soon after the leaves appear and before side stolons form.
    • A tool can be made from wire to do this. Bend a foot on the bottom of the wire and a loop handle on the other end.
    • Push the foot into the mix alongside the infected plant, rotate the foot under the tuber and lift the plant out.
  • At potting time (when tubers are dormant)
    • A sieve is a great time saver during repotting but at the same time an excellent way to spread virus.
    • Do not shake the sieve when tubers are present.
    • Pick out the tubers as you see them and drop them into a smaller kitchen sieve sitting in an ice-cream container of water. The sand and dirt wash off and falls through leaving clean tubers behind.
    • Use a jet of water to remove any remaining dirt.
    • Pat the lumps of mix in the big sieve to crush them to expose any tubers.
    • Shaking the sieve is the equivalent of sandpapering the tubers, a sure way to spread virus.
  • If several plants are virused it is better to dump the whole pot, soil and all.
  • Refuse new plants that look suspect.

ALL EFFORTS SHOULD BE MADE TO ELIMINATE VIRUS FROM AN ORCHID COLLECTION.

Pterostylis 'Nodding Grace'

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2017 October Cultural Notes

Steve Howard’s October Australian Epiphytes and Terrestrials Orchids Cultural Notes for Adelaide’s conditions.

Epiphytes

  • October sees many native epiphytes finish flowering and shortly it will be the best time for potting on and division as new growths are due shortly. The earlier you start, the more time the orchid has a chance to initiate new growth and mature it in time for next years flowering.
  • Remove spent flowers as leaving them on the plant in wet and humid conditions leads to rot caused by botryitis.
  • Be aware that aphids are in big numbers now and will cause grief to flowers and new growths.
    • Malathion at 1 ml/ litre of water will knock them out.
    • Repeat fortnightly for 6 weeks to break the breeding cycle.
  • Apply lime to plants grown in bark to counteract acidity.

Terrestrials

  • Most terrestrials nearing completion of the season.
  • Start drying off once leaves start yellowing. Keep water up to those staying green.
  • Additional shade helps now as suns intensity increases
Epiphytes in flower (1)

Annual NOSSA Spring Show

Growing Leek Orchids – Is it Possible?

The Native Orchid Society of SA has been involved with the Threatened Orchid Project which is attempting to propagate some of our most threatened orchids.  There has been some success such as Thelymitra epicaptoides (Metallic Sun Orchids) but others are proving elusive.  Marc Freestone, from the Orchid Conservation Project, Royal Botanic Gardens Victoria, is a PhD student who is researching one such difficult to grow orchid genus, the Prasophyllum.

Prasophyllum murfettii sm

Prasophyllum murfettii (Denzel’s Leek Orchid)

To assist with his research Marc has the sent the following request.

CAN ANYONE GROW LEEK ORCHIDS?

South Australia has about 40 species and Victoria about 74 species of the native Leek Orchids, Prasophyllum.  Some are on the brink of extinction.

A major problem hampering efforts to prevent our Leek Orchids from going extinct is that they have proven next to impossible to grow in cultivation.  They have proved extremely difficult, usually not germinating at all, or germinating but then dying soon after.  Occasionally some success has been had (particularly with symbiotic germination) but successful germination trials to our knowledge have so far proved un-repeatable.  Working out how to grow Prasophyllum is critical for the survival of many species at risk of extinction across southern Australia.

To try and change this, I will be studying Prasophyllum and their relationships with symbiotic mycorrhizal fungi.

But I need your help!

I am wanting to hear from as many people as possible who

  • have tried (either successfully or unsuccessfully) to grow Leek Orchids or the closely related Midge Orchids (Corunastylis).
  • have observed Leek Orchids (or Midge Orchids) recruiting from seed in the wild.

If you can help, or know of anyone who might be worth talking to, please contact me at: marc.freestone@rbg.vic.gov.au or 0428 304 299.

(Funding and support for this project: Australian National University, Federal Government National Environmental Science Programme, Royal Botanic Gardens Victoria, University of Tasmania).

I would encourage people to contact Marc with whatever information that you have, no matter how insignificant you may think it is.  Every little bit helps including unsuccessful attempts.

His eventual aim is to be able to work out how to grow them reliably from seed in cultivation.