Can Bletilla Ochracea, Epipactis Thunbergii, Pleione Barcena and Ponerorchis Graminifolia grow in pots with either barks and sphagnum moss or laval rocks?
Bletillas can grow in pots but since they spread, you need to increase the size of the pot each year by about 100%. They need forest loam, with some extra woodchips and ground leaves mixed in. I grow a ton of them and they are very easy if you keep them in the shade, keep their roots cool and don't let them get real dry.
Here's a pic of one little specimen of mine.
The answer is yes but combine all your listed ingredients!
I am testing what I call Debris Mix on Pleione, Bletilla, and Epipactis species. So far all seem to be doing ok.
I have the Pleione and the Bletilla crowded into small net pots and/or 4" square plastic pots. I have flowered them but the slugs got the flowers before I could get a good image!! the Epipactis is in a one gallon regular pot as I
repotted when they started growing this year. All look good and the E. gigantea is in flower.
You should water with good quality water. I use r/o water.
Also fertilize when in growth-I use liquid MiracleGro as it has a formula of 12-4-8 which is good for growth and will not burn and can be used frequently (I am rather haphazard about feeding-it happens when I remember!!).
Flowers look very nice.