The Japanese maple tree's tough seeds require patience and care to germinate. The seeds must experience a cold stratification in order to germinate. The easiest way to achieve this is via refrigeration, which keeps the seeds at a cool 38 to 40 F. Some seeds may germinate after planting while other seeds may germinate the following year, according to Sooner Plant Farm.
Collect seeds in the fall, and store them in a bag until 100 days before the last frost date for your region or longer. You cannot plant the seeds outside until frost danger has passed.
Soak Japanese maple seeds in a bowl filled with lukewarm water overnight when you've reached 100 days prior to last frost date. During the night the seeds should sink to the bottom of the bowl. Discard any seeds that are still floating in the morning. Drain out the rest of the seeds into a small colander.
Place the moist Japanese maple tree seeds in a plastic bag filled with equal parts of sand and peat. Seal the plastic bag and place it in the refrigerator. Leave it in the refrigerator for 100 days.
Remove seeds from your refrigerator after 100 days to plant them outside. Sow seeds directly on topsoil, leaving 3 to 4 inches between seeds. Cover over the seeds with 3/8-inch of soil.
Water the newly planted seeds until the soil becomes moist but not saturated.
Allow the soil to dry out thoroughly before watering the seeds again. If you water the seeds too often you may slow down or prevent germination. Continue to care for the seeds in this manner until they germinate.