Someone posted a followup on a message I placed last July on Gardenweb.com about Japanese maple seedlings. The followup asked for more advice about stratifying the seeds and getting them to sprout. This guy posted a response about his method of sprouting them, and it sounds faster than what I did in 2007. He also has some advice on a potting medium and fertilizer for the young plants:

The easiest way to germinate JM seeds that I’ve found is to soak the seeds for 24 hours then place them on moist paper towel in a sandwich plastic container with the lid on. Put the container in the fridge. Depending on the species, the period of time varies in the fridge before they start to germinate then you can simply place seeds in 50/50 perlite and peat moss mix at room temperature till they are a couple inches then place them outside (that’s what I use in Rootmaker starter tray) then 3 parts pine bark fines, one part expanded shale and 1 part peat moss for 1g or larger when they are ready to be potted up. Green JM seeds took a few weeks to germinate in the fridge. Shantung maple seeds took the least amount of time to germinate. Red JM takes 2-3 months. Trident maple takes around 2 months. This is based on Deno’s work. I much prefer this. A lot less messy and reduce space as well.

If you somehow get your hands on Micromax and Osmocote 18-6-12 (9 months) and 17-7-12 (12 months), you get better growth. It’s tough to get them because I’m not “commerical” grower. I use Dynamite 18-6-8 (9 months) from Lowes or Home Depot which seemed to do decent job.