Monthly Terrestrial Orchid Culture – February

The following article by Les Nesbitt is from Journal of the Native Orchid Society of South Australia, February 2019 Volume 33 No 1. It is the first of a monthly series that Les is planning to produce for this year.

It should be noted that February in Australia is late summer and dry; and that this article has been written for Adelaide growing conditions. Many of the terrestrial orchids have been dormant.

Terrestrial Culture — February

The excitement is building with the new growing season about to commence. First leaves on the early species may show this month so start looking. Look with your eyes not your finger. Many a new shoot has been broken by that dastardly finger. Keep the blue tag pots moist. Blue tag orchids include Diplodiums, Ptst. baptistii and Corybas hispidus, all species from the East Coast of Australia.

Repotting and Watering

Finish repotting as soon as possible. Many tubers start shooting this month and are easily damaged by handling. Move all pots to their growing positions for the coming winter. For local orchids adapted to a dry January-March, commence watering in the last week of February and increase watering in March. The water will run down the side of a dry pot and out the drainage holes leaving a dry plug of mix in the middle where the tubers are. Watering three days in a row should wet the pot right through. Continue light watering weekly, so pots do not dry out completely again. Top up the cut she-oak needle layer on pots as needed. This is very important for the fungus dependent species which do not get repotted often.

Diuris tricolour in pot
Topped with she-oak cuttings

Hunting the Grubs and Slugs

Start the nightly visits to pick off the slugs, snails, earwigs and grubs. Hunts are more successful on cooler nights after rain or watering. If the new shoots get eaten off as soon as they appear you might not even see them and wonder why your orchids did not come up.


If the names on labels are starting to fade rewrite them before the name is lost. Remember to pot up any spare tubers for raffles, stalls and the tuber bank later in the year.


The cauline group of greenhoods (Diplodium) from the eastern states are the first to shoot and ideally should have blue tags and have been repotted in January with watering commencing at the end of January. There are some 38 species in this group. Some come from high altitudes in NSW/Vic and start flowering there in February. They flower in March/April/May in Adelaide.

Diplodium in cultivation
Diplodium robustum – one of the cauline greenhoods, with both flowering and non-flowering plants

Points to note about Diplodiums:

  • Flowering plants look different to non-flowering plants. Flowering plants have small pointed leaves on the flower stem. Nonflowering plants have a rosette of rounded leaves flat on the ground. Usually there are only a small percentage of flowering plants.
  • They flower early in the growing season. Most flower in autumn with a few stragglers in winter. None flower in spring.
  • The rosette plants multiply and are easy to grow in regular terrestrial mixes. New tubers form in Autumn.
  • Diplodiums are not easy to flower in Adelaide. Flowers abort if too hot and/or too dry. Grow them in the coolest shady area there is. Keep pots shaded until late March. Local species are easier to flower as they flower in winter.
  • Poor tuber development from flowering plants is common. These plants sometimes die after flowering.
  • Flowering plants can be tall & slender and may need supporting with a wire cylinder. Stakes can damage the developing new tubers.


For additional information on growing terrestrial orchids click here 

A Timely Reminder

This article is reprinted from  Volume 39 No 11 December 2015 Native Orchid Society of South Australia Inc. Journal

Tuber Repotting Time is here

Les Nesbitt

Now that Australian terrestrial orchids have gone into dormancy it is time to think about repotting and preparing for the next growing season.

The best months for this activity are December and January.

I will limit this discussion to the easily grown colony forming terrestrial orchids as these are more likely to be available – for easily grown terrestrials, click here.


We need more terrestrial growers in NOSSA to feed the tuber bank and to supply spare pots for sale to the public at the Spring Show. I found it embarrassing to see so few terrestrials for sale at the 2015 Spring Show compared to the numbers available in years gone by.

Growing terrestrials is a rewarding hobby that does not take up much time or space and will pay for itself. Plus you are doing something effective orchids and the environment even if only the most common terrestrials are grown (eg the greenhoods and onion orchids). Consider easily grown, fast multiplying, Pterostylis curta (listed as rare in the SA Act) has been widely grown in NOSSA collections since the days Roy Hargreave’s wash trough when NOSSA was formed.

Once the basic principles are understood it to move onto the rarer species as artificially propagated plants become available in future as they surely will. Members can draw on the tuber bank in December to get started seriously about it as a group of volunteers will be needed within a year or two to help look after the output of a number of projects already underway or about to start.

Year 8 girls at Kildare College have been repotting the school’s terrestrial collection and this is how they did it.


Prepare all the materials needed including:

  • Pots
  • crocking material,
  • sand
  • organic matter
    • blood & bone, native compost, chopped up sheoak needles
  • 4B pencil and labels.


  • Water the pots lightly a day or two before repotting. The mix should be damp enough to not be dusty, yet dry enough to not stick to everything.
  • Remove the label, wash it in a container of water and stand it aside to dry.
  • Check on the label back to see how many tubers were planted last year.


Scrape off and dump the top layer of soil as this can be contaminated with moss, slimy bacteria and liverworts.

  • Tap out the plug of soil into a sieve sitting on a bowl. Pick out any tubers that are visible on the outside of the plug.
  • Gently break the soil apart and search for tubers while squashing the lumps of mix through the sieve.
    • Very small tubers may go through especially with Corybas. If you have not got a sieve do this operation on a sheet of newspaper.

Place the tubers in a dish so they do not roll away.

  • Count the new tubers to see whether they increased by 2, 3 or 4 times.
  • Discard anything left in the sieve (old tubers, roots etc.).
  • Work out how many new pots are needed to plant all the new tubers.

Add to the old mix in the bowl

  • a pinch of blood & bone,
  • a handful of sand and a handful of native potting mix.
    • Also add enough of these ingredients for each additional pot and mix the contents of the bowl together.

Select new or sterilised 125 mm standard pots

  • and place a square of shadecloth in the bottom to keep the sand in and critters out.
  • Pour in mix to within 30 mm of the top and ram down with your fist.
  • Place up to 10 tubers on top of the mix.
    • Lay tubers horizontally if unsure which is the top.

Labelling and finishing the task

  • Write out the orchid name on extra labels and fill in the numbers of tubers on the back for each pot.
  • Almost fill the pot with mix and tamp down.
  • Insert the label. Place a layer of cut sheoak needles on top of the mix.
  • Water the pots and the job is done.

For show pots use 175 mm or larger pots and plant 20 to 50 of the largest tubers available.

If the tubers have decreased or look unhealthy, throw out all the old mix and replant in new mix.

Repotting a Diuris

Related Articles:

Growing Terrestrial Orchids Part One of Four

Growing Terrestrial Orchids Part Two of Four

Growing Terrestrial Orchids Part Three of Four


%d bloggers like this: