I have grown California Poppies (shades or peach and orange) and Shirley Poppies (red, pink, and white shades). They are very easy and very beautiful for the short time they last here in the South. They might very well do better where you live. We sow them in the fall here, but I would expect you'd sow them in very early spring as far north as you are. If they are happy, they'll self sow from year to year.

I have grown the same here plus some other annual types here in roughly the same zone. They are indeed very easy. I sow directly in March when the garden beds seem just somewhat recovering from the winter and rake them in a bit. In my experience the orange California poppies are the most robust (the other colors which are typically more expensive never do as well). I have grown many different Shirley Poppies and they all do well until they poop out later in July. They reseed here a bit but not enough to keep me from buying more seeds every year. I have tried treating them like wildflowers and scattering seeds in the wilder areas of my old mostly wild yard. This was not successful. They do seem to need tilled soil here and some looking after.

I'm just north of Jackie in NH, and I also direct-sow them in March. If there's snow, they simply get broadcast over the snow. If no snow, a VERY slight raking into the soil so they aren't rolling all over the (possibly still frozen or hard) soil.

I sow many MANY styles of poppies, and never have issues with them either reseeding or having plenty of seed for next season. I did make the 'investment' first year with a gal over on eBay who had myriads of poppy styles for sale (seeds)...lemme see if I can find her username over there. I probably spent $50 for all the individual varieties I bought from her, but the service was excellent, and I had no problems with any of them.
Here she is: onestoppoppyshop She has a 100% rating, and is a good seller.

Enjoy!!!

I have found Wildseed Farms to be a good economical source for annual poppy seeds. I have grown poppies many different ways - indoors, winter sown, direct sow, sowing direct later in May or even June but have found that they do best when sown direct very early.