Move to Alaska?
My opinion is: there is no way to prevent them from returning.
The best you can do is to weed them in early Spring.
They set so many seeds and the seeds are in a pod that explodes when it dries out enough, which scatters the seed quite nicely. So if you're talking the CA poppy with orange flowers and silver/blue foliage, that's the scoop.
Me, I just selectively edit them in my yard. This year I let quite a few stay. They look excellent when Spanish lavender (dark purple) blooms with them. If I get tired of them or they sprawl too much, out they go. No worries, they return in August for another round of blooms.

I dug up a bunch last year right after flowering. I only had to pull up about 3-4 this spring.
But if they are elsewhere in your neighborhood...I guess just keep yanking when young.
It's the same problem I have on my slope with the wild mustard. It's everywhere else and just blows around.

Oh, yes. They're the orange poppies, and they are everywhere... Even growing sideways out of the cracks in the side of a raised deck/patio. I guess I'll just cross my fingers, and hope for the best!

deep___roots~ I may need to steel your phrase, "selectively edit." That cracked me up.

If you've let them go to seed, then it may take a few years of pulling them up in the winter months.

If you don't want something to reseed, the best method is to cut it off before the seeds ripen.

If you want to eradicate it, then pull the tiny plants in late fall, winter, and early spring before it has a chance to bloom and be judicial about if for at least 3-4 years and each time you disturb the soil to replant something else.
Also you can use 2-3" of mulch and a pre-emergent such as "Amaze".

Wanda

And remember that the bees love them, so it helps to leave some around to support declining bee populations.

Corn gluten meal will allegedly prevent seed germination but will not harm existing plants, so in theory spreading some around in the spring will at least lower the number of poppies you have to remove. I admit I've never tried this although I've meant to, and those poppies are really tenacious...

This supports my theory that "weed" is any plant that is too easy to grow.

I would love to have this weed problem.

Alas, the gophers eat all of mine.

I have one clump planted in a chicken wire lined hole.

What?? You don't want our state flower in your garden??? I'm having a hard time understanding that one....

It's illegal to pull up California Poppies, even in your own yard. I sure hope you don't let your neighbors see you pulling them up. You could get a heafty fine.

tressa~ Although the CA poppy is a nice looking flower when in bloom, I find the rest of the plant to be pretty ugly when there aren't any flowers. Also they spread like, well, wildflowers, and had taken over a 2'x24' section of my yard that will look sooooooo much better with different plants there. That's why I don't want the poppies there.

mentha~ It may be illegal to pull CA poppies from a roadside display or the woods, but it's silly, IMHO to think you can get in trouble for pulling them from your own yard...

quote:
"A common misconception associated with the plant, because of its status as a state flower, is that the cutting or damaging of the California poppy is illegal. There is no such law in California, outside of state law that makes it a misdemeanor to cut or remove any plant growing on state or county highways or public lands except by authorized government employees and contractors."

Here is a link that might be useful: CA poppy info

Tell that to my uncle who got a $3000 fine for mowing them down not too long ago.

The landmanagement district contracted by my city to remove brush weed whacks them. I complained and they said they weren't seeded by them there so it was legal.
But at least by the time they come along to do it they have mostly gone to seed.