Carnivorous Plants/Soil for pings
In your DVD, I saw that you can use pure minerals (vermiculite, pumice, perlite, etc.) to grow Nepenthes. Can you do this for Pinguicula laueana? I have a cutting in pumice that is just putting out its first leaves, and I want to know if I can keep it in pumice. It will be under a fluorescent light that has been used before on Nepenthes and pings with very satisfactory results. If I couldn't do just pumice, would one part live Sphagnum and one or two parts pumice work?
P.S. I can't figure out how to water Pings. I have been putting them in 1-1/2 inch of water (purified), and letting the tray dry completely. It seems to have been working, but I have only been using this system for a short time.
You can grow them in a pure mineral mix, but we've found over the years that we get the best results when they are in a peat/perlite/sand mix. Pumice could easily be used in place of the perlite. The peat provides some moisture holding properties, and some tiny nutrient amounts, and the mineral mix gives give good root aeration an keeps them from being too wet. Our typical mix is 1 part peat, 2 parts perlite or pumice, to one part sand. Don't skip the sand. It really creates an environment that their roots like. To that we add 1 tablespoon dolomite lime per cup of soil. (available at almost any garden center; use regular, not prilled) Most Mexican Butterworts grow in limestone or gypsum in nature, so the are used to an alkaline soil. We saw a dramatic difference in growth of some species when we started using the lime. Because they do like it alkaline, I would not recommend live sphagnum.
With watering, keep in mind that Mexican Pings are not bog plants. They grow in seeps on hillsides as opposed to having the high water table of a bog. For that reason setting the pots in water isn't a good idea for long periods. They do best if you top-water them. I like to water a plant until I get some runoff, then stop. I don't like to leave any more than 1/4 inch of water in a tray. In summer when plants are going through lots of water and it's hot, it's ok to have a little more in the tray, but they really should only have moist soil, not sopping wet. They will tolerate some drying too, but if you keep them too dry, they'll often go dormant. Just get in the habit of feeling the soil. Feels wet, or you still have a little water in the tray? Leave it alone. Top of soil feeling a little dry and the tray is dry? Top-water till things are wet.
Bigger pots will also make this much simpler. A large pot holds more moisture, and keeps the plants higher out of a water tray. This helps to avoid rot if you do happen to have water in the tray for a bit longer than you expected. Here's a good article: http://www.carnivorousplants.org/howto/GrowingGuides/Pings_Mexican.php