There is a wide pattern of germination among the maples.
The seed of many Acers benefit from being not being allowed to dry after collection. Some species (Asian species in particular) also benefit from slightly early collection between green and fully ripe and then moist-packed. Doing this will often produce germination after one cold treatment, rather than two or more (Acer palmatum, sieboldianum, pseudosieboldianum, japonicum etc). These often have multiple seed coats.
Then, of course are species whose seed is short lived (Acer saccharum) or that are instant warm germinators (Acer rubrum etc.)
My tendency with seed is to ignore the popular germination references that are easily available on line, unless they are from sources where the work/research has been done by the individual posting the information using scientific methodology. While simple observation of seed germination is one thing---it is often coloured by too many other factors to be accurate or something that can be replicated.
While the on-line germination guides can be a helpful starting point, they are often, as I have said before, simple repetition of erroneous, or incomplete information.
Take for example, on-line information on Acer carpinifolium germination---which will be in 99% of the cases, a simple repeat of what is found on Tom Clothier's germination data base, to wit:
Tom Clothier:
"Acer carpinifolium sow 4 wks @ 70ºF, move to 39ºF for germ. in 3 to 6 months"
Thus, while it may be true that if you follow this guidance precisely and provide cold immediately after the 4 weeks warm, germination will follow as promised, this is hardly the correct picture of how this species germinates.
In fact, kept moist and at warm for just over the 4 week point (and not by much) germination is massive and is at warm---which should make this species a propagators dream. The cold is hardly required at all, unless the seed is dried first, I suspect---but only my next set of tests with dry seed will determine that.
One has to balance all I have said with what happens naturally in the wild, of course. Is there ever enough warmth and moisture remaining in it's native haunts to induce timely germination so soon after seed drop. Also, how dry will be seed be, once it has dropped, compared to being artifically collected by a human hand before that time, and sown immediately????
There are a multiple of factors to consider.
In any event, here is my simple proof of the first proposition. Acer carpinifolium collected when ripe (not green) and sown (or moist packed in my case) fairly soon after collection (within a month) germinates quickly at warm
(4-6 weeks or less).
