here is Eric Partrat's method of growing P. vallisneriifolia
http://www.pinguicula.org/pages/plantes/pinguicula_vallisneriifolia.htm. He grows it in a pure mineral substrate.
Yes, he is from France. Also "jeff 2" on this forum is from France and suggests pure mineral substrate for several Ping species. But I'm not yet convinced. In my area (Northern Germany) the winter temperatures go much lower than in France. We may have sharp frost with no snow covering for several weeks each year. Lowest temperatures drop to -15°C = 5°F each year and some winters even lower. My concern is, that if a substrate cannot hold enough water, the winter buds will be freeze-dried and not survive the winter months. I just use a thin horticural garden fleece during frost periods to protect the mini-bogs while no snow is present during heavy frost.
Of course I can (and will or even must) do more experiments on substrate, but unfortunately it is very time consuming to do tests: Only if a substrate proves to be suitable for use in summer AND winter, it is really a good substrate. For hardy Pinguicula the life cycle through the whole year is essential, not only a few months during spring or summer.
I think if you have spare gemmae, it would be worth trying both methods to see how they do.
If I'd purchase more portions of gemmae, I could do more experiments with P. vallisneriifolia. Unfortunately I will not be able to have good success with harvesting gemmae of P. vallisneriifolia myself, from what I have seen on growing my plants this summer. So my experimenting will be limited. Especially because I also want other temperate species to establish in my mini-bogs.
Next spring I will have twice as much of P. grandiflora ready for flowering as this year. And another species looks promising currently: P. spec. "Rio Ara". They seem to like the same conditions as P. grandiflora does. Meaning that they grow in pure peat as well as in the same mineral mix that I posted in my posting above. P. spec. "Rio Ara" can develop nice reddish leaves under a bit of sun. I still must prove whether they do well during the winter in my climate.
At the moment I do not put all eggs into one basket with my hardy Pinguicula. I try to grow different species and do my observations, what's growing easy and what's not in my garden.
I propagate what's easy for me, until I have a full mini-bog of them under those conditions that have proven to be all right. I try one or two new species and hybrids each year. And I retry one or two species that I could not keep alive in earlier years by varying the conditions (like substrate and more).
I got a dormant bud in May, and plan on growing it under lights soon in a pure mineral substrate. This is a harder plant to cultivate, so it may be picky with the conditions we give them.
Perhaps I should visit the plant nursery some day, where I purchase my gemmae of hardy Pinguicula. It is also in Germany, only a few hundreds Kilometres away. Perhaps I can find out what they do to cultivate and propagate P. vallisneriifolia successfully. I think they are using their greenhouses, at least for some time of the year.
Your P. macroceras look awesome!!! I've had a lot of the seeds you sent me germinate sporadically, and I think with winter coming up, it might give the rest a chance to stratify, so I think I'll get more in the spring.
I have also sown some seeds of P. macroceras (although I have enough plants). A good fraction of them is germinating without cold stratification. I keep the seed pot in my cellar under LED lighting, I'm guessing the first germination starts after 4 weeks and it is stretching over a long time. I think between 4 and 12 weeks after sowing there will be a germination rate of 25 or 30%. That's BTW the same as with P. grandiflora, they will even show a bit higher germination rate without previous cold stratification (at least when the seeds are fresh).
But with P. grandiflora the germination without stratification may already be a "positive selection", because I already grew the mother plants from seeds - without stratification.
I'm looking forward to having a bog garden that looks like yours full of temperate pings!
Best wishes!