How to: pot up Blunt Greenhood Orchids (Pterostylis curta)

Growing orchids isn't for everyone. But there are many interesting orchids native to the Illawarra, and some of them are really quite simple to cultivate. Here's a quick and basic how-to on repotting Blunt Greenhood Orchids (Pterostylis curta), probably the easiest local ground orchid to grow. The same technique can also be used for most other local Greenhood Orchids.

Blunt Greenhood Orchids that have been growing in a pot for two years. Image by Emma Rooksby.

If you're lucky enough to get hold of a plant in a pot, that's a good first step. Enjoy it! But 1-2 years after that it will need to be repotted, to give it room to grow and provide fresh soil that will help it flourish. It will have produced new tubers below the surface, and repotting will allow you to separate these out and grow new plants from them.

Repotting is best done in summer when the original plant has died right back and the leaves are more or less invisible.

My pot of Blunt Greenhood Orchid in December 2018, showing the leaves more or less dead. This plant is ready to pot up! Image by Emma Rooksby.

Step 1: Preparation.
Before you start you'll need to prepare a bit. Gather yourself:
- 1 or 2 extra plant pots, ideally low pots specifically made for growing orchids. If you don't have those, take a regular plant pot, and cut it down so the side walls are about 10cm high.
- potting mix
- river sand
- well-rotted native plant humus (optional extra)

Here's a tray holding the mix I used. 60% native plant potting mix, 20% river sand and 20% well-rotted humus from the local Blackbutt trees. Image by Emma Rooksby.

Step 2: Extracting the tubers from the original pot
Blunt Greenhoods grow from an underground tuber. After a decent year of growth, the plant will produce a few 'daughter tubers,' that grow out from the main tuber via stolons. These are what you will be moving into the new pots.

Water the original pot well. Next, turn the pot upside down, very gently, perhaps onto your tray of potting mix, and tap it to encourage the soil to fall out in a single mass. You will probably see quite a few daughter tubers growing around the edge of the soil mix, particularly if it has been a good year.

This shot shows the soil that has come out of the up-ended pot - the small creamy-white spheres are the
daughter tubers. They were mostly clustered around the edges of the pot, towards the bottom. Image by Emma Rooksby.

Step 3: put the tubers into new pots
Once you have extracted the tubers it's time to put them into new pots. Before you do so, gently separate the tubers from the soil they were growing in and mix the soil into the potting mix mixture that you've prepared. This will ensure they have some of their original soil with whatever soil magic it contains.

Fill the new pots to around the 1/4 full mark with your prepared potting mix. Place the tubers gently onto this soil layer, and then top the pot up with more of the potting mix. Water in well.

Orchid tubers potted up. The leaves in these two pots were added merely for decoration. They had more or less died off, but I left them on top of the soil to remind me of the good growing season these orchids had had in 2018. Image by Emma Rooksby.

Step 4: Ongoing care
I haven't potted up this species before, but they need to be kept moist, not wet, during their period of dormancy (through to autumn). Once they put out new leaves, more regular watering and the occasional application of very weak liquid fertiliser may help them thrive (though I have never bothered with this!). With luck your orchids will give an even better display than they did the year before.