Monthly Terrestrial Orchid Culture – April

The following article by Les Nesbitt is taken from the Native Orchid Society of South Australia Journal, April 2019, Volume 43 No 3

Terrestrial Culture – April
Les Nesbitt

The days and nights are cooling down, evaporation rates are dropping and pots take longer to dry out so decrease the watering. If in doubt wait another day before watering. Regular rain usually begins around Anzac Day. There is nothing like a good rain to make terrestrial leaves pop up almost overnight. A few early flowers are out this month – Eriochilus species and possibly Pterostylis truncata. Keep up the pest control and pull out weeds while they are still small.

Sow seed on pots around mother plants of fungus dependent orchids this month. Mix seed & fine sand together to avoid wasting precious seed. A pepper shaker helps spread the seed evenly. Water gently to wash the seed into the mulch.

April is a good month to deflask terrestrials. Seedlings need to establish & harden up before winter so get deflasking completed by the end of April. Check out flask suppliers for that special species. The next deflasking opportunity is early spring.

Deflasking Terrestrial orchids

Prepare a suitable soil mix for the orchid to be deflasked along with labels & sheoak topping. Use the same mix as for adult plants.

Select a flask with strongly growing seedlings, preferably with small tubers but plants without tubers are OK. Remove the flask lid and tip the mass of plants and agar into a fine sieve. If you are nervous remove clumps of plants from the flask with tongs. Try to minimize breakages. The junction of leaf & tuber is very weak. Over a sink or lawn, use a jet of water to wash away the agar leaving clean seedlings behind.

Fill a pot with mix to within 2 cm of the rim and tamp down. Select small clumps of seedlings and stand them around the edge of the pot. Insert a label with the appropriate info as this pot will not be repotted for 2 years. Pour a handful of mix into the centre of the pot and gently squeeze mix out around the seedlings just covering the bases but not burying the leaves. Add more mix if necessary. Tamp down the mix in the centre of the pot. Add a layer of chopped sheoak needles. Water gently to settle the mix around the seedlings.

The pot can go into the shadehouse with other terrestrial pots although it helps to keep all the seedling pots together in a sunny place with good air movement. Ensure the pot does not dry out. If kept too wet the seedlings may rot. If the seedlings establish and grow strongly they can remain in the shadehouse over winter. At any sign of rot move the pots out of the rain under cover and water by standing the pot in a saucer of water.

Next dormant season as soon as the leaves have died down, add more mix to completely fill the pot. This helps to protect the tiny seedling tubers from drying up in the heat of summer. After the second growing season the tubers should all be large enough to find easily at repotting time.

Q&A: How do I deal with mould in my orchid flasks?

Question:

I have recently been learning about propagating orchid via flasks but I have mould in some of the flasks.

Orchid Seeds in flask with mould
Flask with orchid seeds and mould

There is mould in the flask with orchid seeds and also in the flask with Diuris tricolour in bulbs.  The bulbs are almost ready for deflasking.

Diuris tricolour in flask
Flask of Diuris tricolour (no mould) – these will be deflasked later this year.

 

What can I do?

Answer:

With a home laboratory, no matter how careful one is, mould can still contaminate the jars of agar. If mould occurs when the orchids are still in seed, then the whole jar needs to be discarded.  The seeds will not survive.

With the Diuris flask, as they are almost ready for deflasking, pot them out straight away. This needs to be done within 10 days of the mould appearing. The weather (March, 2017, South Australia) is still a little too warm but if left in the flask, the plants will die.  Potting them out may give them a chance of survival.

When deflasking, it is important to rinse all the agar off the bulbs before potting on as normal. Once potted, it could help to cover the pot with a cut down clear drink bottle with the lid removed. This will allow some air to circulate. Keep the pot in a shady spot.

Diuris tricolour in pot with bottle top cover
Potted Diuris tricolour with protecting bottle cover

Will it survive in the pot? Hopefully it might but at least the plants have a better chance of survival then if left in the flask where it would surely die.