A quote from the Petiolaris man his own self:
I grow Dilatato-petiolaris in 70% perlite, 30%
spaghnum. They like a very airy mixture. So whatever
medium you're using, take it easy on the peat. In
nature, Dilatato-petiolaris grows in very alkaline
soil. Also, grow all Petiolaris moist, not wet. It's
better to grow them in small containers, because small
containers heat up faster. Outside this is how I grow
my Petiolaris in Spring and Summer in Los Angeles,CA
: I grow them in 4 inch square pots, standing in water
with a two-liter bottle put over the top of them.(A
two-liter bottle fits perfectly into a 4 inch square
pot and makes a perfect little dome.) Then I give them
all-day sun. It gets so humid inside that I can't see
inside of it, but a little thump on the bottle causes
the water to go back on the plant and in turn, they
get a little gentle tropical rain for my babies.
Petiolaris Sean
He also said for the seed, use the same medium and he does not use GA3 on the dilatato-petiolaris.
Cheers