I have done it once via the winter sowing method. It took two years, i.e., the first summer nothing, and I just put the container in the shade and let the natural rain water it.(Sure glad it was not this summer!) I closed it up in the fall, and the following spring I had the one leaf sprouts. I have put them in the ground, and we shall see next year if they return. If you can sow the seeds fresh, you will have a better chance, even tho' it will probably take two years, too. I got my seeds from NARGS, so they were dry. Some people use the chilling in the frige method, but I never have that much room, so I don't do that. Either way it is a long process, requiring several steps. That is why they cost so much! I have had trilliums long enough so that I am now seeing "babies" out in the garden. Yeah!!

Trillium seed should be kept moist after harvest, dry seeds are hard to germinate.

It requires cold moist stratification before it will germinate. You can store the seed in moist vermiculite in a baggie in the fridge for four months before sowing or sow in seed tray and leave outdoors for the winter.

It has double germination: the first spring and summer the seeds grow only roots. After another cold period and in the second spring the seeds with roots will germinate a single leaf. It will be three to five years before the plants are large enough to flower.

Here is a link that might be useful: Propagating white trillium

it can take 6 years from seed to flower

See the link below for a published protocol.

Previous posters are right: you will not see anything above ground for two years, and you are probably 5-7 years away from flowering.

Not extremely difficult in the right climate, but requires patience.

good luck!

Here is a link that might be useful: Trillium propagation