Collecting Japanese Maple Seeds

When is the recommended time to collect/harvest seeds from Japanese Maples?

late fall when they are ready to fall off and dried out

Are the ones that have recently fallen any good?

they should be fine if they fell of on their own

Merrymath, you will save yourself some frustration if you do a cut test. I picked some for 2 years, different trees miles apart, and some had only 5% viable seeds. They look exactly alike, and some even sank in the float test. If you have extras, cut them in half and see how likely you are to get anything to grow.

What process did you follow to try and start the seeds? I think JM seeds require double stratification or something along those lines that's more complicated than what most seeds need, so if you didn't do that then that could explain the poor germination vs the seeds themselves not being viable.