As far as I know L.formosanum has an immediate epigeal germination= no special treatment. Just sow and wait.

You can check the link below

Here is a link that might be useful: Types of germination.

Lily seeds are a devil to germinate. It's much easier from offsets but, if that's not an option, here goes. L.formosum is from China and in nature is subjected to extremes of temperature. Place the seed in damp, sterile sand and leave for 3 weeks at a warm temperature. Then place in the fridge or outdoors in northern USA (winter) for a further month. Bring back into the warm. If they don't germinate after a further month, repeat the process. They don't need to freeze but it doesn't matter if they do. Good luck. - Ian.

Unfortunately, the procedure described above does not apply for Lilium formosanum. Firstly, L. Formosanum as the name suggests is from Taiwan(former name Formosa), which has a subtropical climate, so no chilling necessary or advisable. Secondly, the procedure described by ianbrazil applies only for lilies which have delayed hypogeal germination. Here we have a rapid epigeal germination(= total oposite).
Thirdly, L.formosanum may not be totally hardy in your zone. Subspecies L.formosanum pricei may be a triffle hardier.

Sorry to come back, but I am correct. Lilium formosanum is found on Mt. Hehuan in the central mountain range at high altitude. The climate there will be cool temperate not subtropical and it is in fact hardy down to UDA Zone5. Temps will vary considerably so I still think the warm/cool/warm treatment will work best. - Ian

Even 10 years ago when I had real zone 4 winters, L. formosanum v. pricei is winter hardy. In fact certain clones of L. formosanum are hardy enough, too. The species clearly has inherited more cold hardiness then it needs in its native lands, both subtropical and alpine.

Whether the germination mode is immediate epigeal (IE) or delayed hypogeal (DH) has little to do with the actual germination of the seed. Unless you are talking about western American species or a few others that germinate best at 50-60F (10-15C), all lilies germinate at about 70F ((21C). The difference is that IE seed emerge above ground without an ensuing cold treatment. DH seed require a cold treatment to produce a leaf. That said, a cold treatment before germinating IE seed at warm temperatures is often beneficial and can result in more uniform germination of multiple seeds.

I have grown L. formosanum v pricei seed several times. I have had it come up without any cold treatment by planting directily at 70F, but most often, nothing happens until I give it a cold treatment, and then bring it into the warmth.

Some really good advice above. Having a broad applied, working knowledge of the species goes much further than one line in a reference book. Giving so called immediate epigeal seeds a cold treament first won't hurt them--it will help them. It's a fairly common practice used by pollenaters and seeders on more difficult, stubborn or unique epigeal seeds. So, rcharles, if you've already sowed a batch and they don't sprout in 30 days or so, give them the cold treatment--then return to 70'F for germination. You will be pleasantly surprized! Or if you have more seed left, sow another batch and cold treat first. Again, some very, very good advice, above.