Coming from a very different zone, nigella and annual poppies are two things I always direct sow.

California bluebell is common name for more than one plant -
California Bluebell Phacelia germinates at lower temps (55ish) so may do better outdoors, that's not a good temp for me to achieve anywhere indoors
California BlueBell Nemophila germinates better warmer, more like 70F

Another good reason for using the botanical names. Now you have my curiosity.

Sorry, it's definitely the Phacelia. Good to know about the lower germ. temps. for the Phacelia. So direct sow for that one then...

I can only speak about starting poppies. They are best direct sown. Start well before March. Now, or as soon your snow is less than 4" high, go out and throw the seed where you want poppies to grow. They don't mind freezing and they don't need to be covered by soil. When the day length and temperature are right, they will germinate. Next year shake the dried seed pods around wherever you want poppies and wait for them. Poppies are easy.