Japanese Maple seeds have a very hard outer coating as do many ornamental plants. Under natural conditions, the seeds would have to be on the ground for almost two years before they would germinate. All that happens the first winter is the moisture softens the hard outer shell, and the second winter germination begins to take place. For all of this to happen in the proper sequence so the seedlings sprout at a time of the year when freezing temperatures or hot summer sun doesn’t kill them, takes a tremendous amount of luck. You can improve the odds by controlling some of these conditions, and shorten the cycle.
Once you have picked the seeds and removed the wing just place them in a paper bag and store them in a cool dry place until you are ready for them. You don’t want to plant your seeds out in the spring until the danger of frost has passed, here in the north May 15th is a safe bet. If May 15th is your target date you should count backwards on the calendar 100 days. That will take you to about February 5th if my math is correct.
On or about the 100th day before your target planting date, take the seeds and place them in a Styrofoam cup or other container that will withstand some hot water. Draw warm to hot water from your kitchen faucet and pour it over the seeds. Most of the seeds will float, just leave them in the water overnight as the water cools down. 24 hours later most of the seeds will have settled to the bottom of the cup, drain off the water. Place the seeds in a plastic bag with a mixture of sand and peat or other suitable mix. Even light potting soil will work. The peat or soil should be moist, but not soaking wet. Poke some holes in the bag so there is some air circulation, and place the bag in yourRead more on backyardgardener.com