My neighbor has a Red Japanese Maple with thousands of seeds. If I harvest seeds this October how long can I keep them and still have good germination? John
They can germinate for several years. In fact, if you sew them out you will likely get only 30 percent or so germination the next spring. Then next year you could get around 20 percent, then 10 or so the next year.
But I would suggest following a stratification plan.
Here is a decent explanation of all this mess:
The best way to cold stratify is by soaking the seeds (wings and all) in water for a day, then spraying with fungicide. Then, place them in a slightly moist 50% peat/50% perlite soil mix in a plastic baggy. Then leave this in the bottom of the fridge about 60 days before spring planting date. They should be ready to sew by 90 days.