Collect fresh, ripe Japanese maple seeds. Pull off the helicopter wing attached to the actual seed and store the seeds in a paper bag in a cool, dry location. Seeds need to be planted in spring, after all danger of frost has passed.
Count back 100 days from the date on which you plan to plant your seeds. On this date place your seeds in a Styrofoam cup and fill the cup with hot tap water. Allow the seeds to soak overnight.
Place the seeds in a baggie with a mixture of 50 percent peat moss and 50 percent garden soil which has been dampened but is not too wet. Poke one or two holes in the bag for air circulation and then place the baggie in your refrigerator for 100 days.
Rake the top few inches of your planting bed to loosen the soil. Rake in a bit of peat moss, then lay your Japanese maple seeds on top of the soil and lightly cover with about three-eighths of an inch of loose soil. Water well.
Install a piece of snow fence above your seed bed to block about half of the sun striking your seedlings. Seedlings like some sun but too much sun can burn them. Allow the ground to dry between waterings--this will keep the seeds warmer and speed up the sprouting process.
Allow the seedlings to grow and mature for one or two years before transplanting. Transplant in the fall when the seedlings are dormant.