I noticed your name come up in a few of the sites on gardenweb lily page

Not sure who you are talking about, but I'll jump in.

Martagons are among the first lilies to bloom. White is not too common among the cultivars, but can be had. Most common is probably Lilium martagon var. album. Flower size in inherently small compared to asiatics and orientals. They are lilies that grow well in dappled shade or sun(in the Pacific NW) where they get ample water. Bulbs are expensive because martagons (basically) do not produce stem bulblets, and propagation is thus curtailed. These are one of the lilies with whorled (tiered) leaves. something that could add a lot of interest with your other lilies.

Lilium speciosum var. album is very late blooming. I don't know how well it would perform in Seattle, were summers are cool. Your season may not be long enough. Hopefully, someone will chime in. I just don't know. Very nice lily though.

Lilium cernuum I can't say anything about.

Whether these lilies work for you depends on "how white" you want your white to be.

The white form of lilium cernuum is a creamy pink. Cernuum has a small bulb and delicate grassy foliage and hence should be planted more shallowly than orientals (a few inches only) and in light soil. It does bloom earlier than the orientals and unlike hybrid asiatics has a scent.

Speciosum album is beautiful and easy to grow and will tolerate dappled shade. It blooms at the end of the oriental season, and so will extend your Casa Blanca bloom on the late end if planted together. I do the pink version of this with speciosum rubrum interplanted with Stargazer. It works really well.

For the early end, you might want to consider the easter lily, lilium longiflorum, and its interspecific hybrids with asiatics, LA hybrids. On the east coast longiflorum blooms in June.

For midway between asiatics and orientals you might want to consider lilium regale album. Its a species trumpet lily that is very easy to grow and is readily available. It has an incredible scent, especially in early evening.

lilium cerneum album
lilium speciosum album
lilium regale album

are all being carried by VanEngelen pretty cheaply and in large quantities (but the bulbs are a bit smaller and will take a couple seasons to get going full steam).

Brent and Becky's is also carrying speciosum and regale. They are still a reasonable price and if you check listed bulb sizes you'll see that theirs are a little larger.

-Helen

White Butterflies has a very long bloom tome for me here in MN. It's available from the Lily Garden thelilygarden.com