I am interested in the seed germination requirements of Acer triflorum and Acer griseum.
There is information in The Reference Manual of Woody Plant Propagation by Michael Dirr and Charles Heuser (Varsity Press,2006):
Acer triflorum seed is “doubly dormant and when fall planted will germinate the second spring and sporadically thereafter. Seed, unfortunately, is often not sound […] Nine months warm followed by 3 months cold gave reasonable germination. If seed is received dry it may be prestratified for 6 months and then sown. Germination is less than 1% the first year but is very good the second.”
The authors state that with Acer griseum, “the biggest problem is poor seed quality” (between 1 to 8% viability). Also, seed production from an individual tree varies widely from year to year. “Seeds are doubly dormant and if fall planted require 2 years, some germinating the third year and beyond. The pericarp wall is extremely tough and dormancy is caused by a physical barrier as well as internal embryo conditions.” Dirr says that he has cold-stratified seed for 90 days, split the fruit wall to extract the embryos, and planted them in vermiculite with a fair amount of success. Growing this tree from cuttings is considered extremely difficult, and grafting (onto seedling Acer griseum seems to be the easiest propagation method.