With a little patience though, and by following a few simple steps, you can be very successful and have great results the first season.
Most importantly, obtain the freshest seeds you can find! Japanese maples generally produce seeds in spring to early summer, shortly after small red flowers appear.
They can be collected in late summer to early fall, just as the seeds start to turn brown, or you can order them from nurseries that sell seeds.
You will get the best results from fresh seeds, so be careful of anyone offering "fresh" seeds all year long.
Store the seeds in a cool dry place until you are ready to stratify the seeds.
Stratification is the process of artificially imitating the natural process of winter to encourage the seeds to germinate.
Your seeds will need to be stratified for approximately 120 days, so plan on beginning this process 120 days before the last anticipated frost in your area.
First, soak the seeds in water for 48-72 hours, making sure to change the water daily.
Then place the seeds in a ziploc bag filled with slightly damp perlite or vermiculite.
Some people suggest peat moss or sand and application of a fungicide, but perlite and vermiculite are more sterile than these substances.
I have had no issues with mold developing by using perlite with no fungicide, but it does not hurt to be cautious and use a fungicide anyways.
Place the bags in a refrigerator that is ideally a few degrees above freezing.
If the temperature happens to fall below freezing , just adjust your temp.
setting a bit, and the seeds will still be fine.
Check the bags every week or so for mold , wash off any seeds that you find fungus on, and replace the media in any bags that develop mold.
It is always wise to divide up your seeds into numerous baggies so they are not all together in the event of a mold outbreak.
Start checking the bags for sprouting seeds after about 60 days, and plant any that you find that have developed a small white rootlet.
I have had better luck letting the non-sprouting seeds remain in the refrigerator longer than 120 days, rather than planting them all, if only a few have sprouted.
You can leave the remaining seeds for a few weeks longer, and by then most of the seeds that are going to sprout will have done so.
The rest can be planted in hopes that they will eventually sprout.
Some may not, however, until the following year.
After your seeds sprout, you are ready to plant them in the ground or a container.
Make sure and use a high quality, well draining soil, especially when planting seeds that have not yet sprouted.
Soil should be light and fluffy to allow the seedlings to break the surface.
Compacted soil will result in very few seedlings.
Place the seeds approximately 1/4" under the soil surface and water thoroughly.
Do not water again until the soil has started to dry out.
Soil that remains constantly wet will cause the little seedlings to rot.
The first years growth won't amount to much as the little seedlings are developing their root systems, but by the second year they will have really started to grow and could reach 12 to 18" in height.
It is best to transplant any root bound trees after they have gone dormant.
One thing to note is that seeds from a particular cultivar will not necessarily have the characteristics of the parent plant.
Some may have these characteristics, while some will look totally different.
The only way to have a true clone of the cultivar is by grafting or rooted cuttings.