Hello. I'm sorry that I have no advice for you, but I was wondering from where did you get the seeds? Thanks.

I live in Europe and I bought the seeds from sunshine-seeds.de They sometimes have this species available. I only buy seeds that are listed in the new arrivals ("Neuzugänge") and they germinate well. I think that they ship worldwide but I don't know anything about shipping charges and regulations concerning sending seed to the USA. But if you think it is worth for you to deal with them then check the new seeds regularly.
Feri

I have a couple species of Gustavia including G augusta. They like it hot and humid, and even then their growth rate is pretty slow when small. As they get some size they do speed up a little.

So hot and humid. Thanks for the info. Then a home-made "greenhouse" will be O.K. for them. My Typhonodorum seedlings like it hot too and they stand in water. I will place them together and humidity will be provided by the water of Typhonodorums :)
I have two more questions regarding Gustavia:
1. What is their soil pH requirement? I keep them in slightly acidic soil (sphagnum, regular soil, coconut fiber and perlite).
2. Do they need fungus to make Mycorrhiza, or do they thrive in clean soil mixture?

Slightly acidic, organic-rich soil is fine, but it does need to be well draining.

Popper1's comment about heat and humidity is soooo true.

Thank you for your answer.