Ny,
the trunk grew to 3" in a few months. The tree was firstly grown as a normal tree, under the shade of a Flacourtia tree and after a few years, entered the winter in the fridge cycle.
Our climate, will cool to 70 deg.F from say 6 p.m to 8 or 9 a.m in the months of sometimes as early as October, but normally November and the trident maple responds to shorter days, then the cooler weather.
[ Pot was a 2 gallon and the basic soil we use for all the trees]
By January 21st or so, it is ready to enter the fridge. It never gets the autumn colour, but the leaves drop.
The coolness is enhanced by placing the tree in the north side of the house, and the stone of the house walls continue to cool the air all day long. The north side of the house is in shade from October until the 26th of February.
Tree was removed from the fridge around April 1st and then buds out in May.
Never experienced leaf burn as reported from Miami.
We have no heatwaves, and mild humidity, even with heavy rainfall, the humidity rarely crosses 80%.
So all that was done was mild extensions, and defoliation once a year as the book says to.
The mistake made was too wet a soil. Will be trying again.
In the UK in Cornwall, Marcus Watts [ IBC ], if memory is correct, has his trident in a green house. Cornwall I believe is a zone 9b.
We are unable to provide the chill to complete the dormancy.
Does this help?
Good Day
Anthony