Not full of them, but I’ve always been especially fond of plants, and poppies in particular because my mom grew some spectacular varieties. Through boredom and interest I discovered a home nearby was growing a variety of poppy which could be processed into opium. I took some seed heads at the correct growth stage on an evening walk, then processed them later.

The process is very crude but works well for experimentation. I think if you were a serious opiate user it would probably be too inefficient and inconvenient to warrant over simply buying opium.

It may be legal to grow opium poppies in the US for garden or seed purposes, just not for the processing into opium.

https://depts.washington.edu/hortlib/resources/wp-resource_s...

Michael Pollan also wrote an essay about it (I think taking a slightly stronger position).

I don't doubt it, but are they so common that I might walk by them in my own neighborhood? (I'm asking, I have no idea).

Yes, I still see them while walking around here in Victoria, BC. I have some seeds from a friend as well. They circulate and people grow them out of curiosity as well I guess. You’ve maybe seen them without realizing it.

Perhaps Tasmania? Tasmania has legalized opium production and you'll see fields of opium poppies everywhere since it's the source of the majority of medical opiates. The reasons for Tasmania being the center of the western worlds poppy production are obvious. It's easy to ensure the exports to the rest of the world are done via controlled channels.

This does lead to the weird situation where an entire population has easy access to opium should they want to raid nearby fields; the fields are lightly fenced with warning signs stating that it's bad for your health. Perhaps surprisingly to many Tasmania doesn't really have any issues from this. This may lend some credence to the above article - it takes more than just access to lead to issues for people.

https://en.wikipedia.org/wiki/Tasmanian_opium_poppy_farming_...

He lives next to next to the Land of Oz.