I've not grown Lilium bulbiferum until this year, when a generous NARGS member sent me some bulbils. He didn't have the "ssp. croceum" on the name, but it is likely that is what it is. 90% or more of the L. bulbiferum in commerce are this subspecies. It seems to be very easy to grow for the Europeans in their gardens, despite its native habitat being open meadows, growing tightly with other grasses and plants. But I have nothing to report personally.
As you probably saw, L. bulbiferum var. croceum seed will have delayed hypogeal or immediate hypogeal germination. When you plant them this spring, they will all (or most all) germinate, but some will produce a leaf in the same season (probably in about a month or so), and some will emerge above ground the following season.
There are some small European nurseries that sell select lily seed. If you peruse the Lilium threads on the SRGC forum, you will find mention of them. Many will ship outside Europe. Unless you join as a forum member (free), you can't search the forum, so here are some links:
Lilium 2016
Lilium 2015
Marcus Harvey in Tasmania operates Hillview Rare Plants with Lilium spp. seed. He is well respected.
Bjønar Olsen (trillium.no) sells seed directly from China, but I think he is taking this year off.
