Ordinary spinach, planted in the fall, would usually survive the winter for me in southern Michigan. Of course it would spend 3 or more months under snow and inaccessible most of the time, but it would be there at spring thaw and start right off growing......
It depends on what climate you live in. Sounds like you guys are talking about cool/cold temperate climates.
In hot drylands, spinach will grow here in Phoenix during the winter but as soon as higher temps show up, it bolts. So the greens that are hardiest for us are prickly pear (Nopales). I've seen them when it's 122 degrees (wilting) and I've seen them with snow on them.
Subtropical desert (Köppen: BWh)
Elevation: 1090 ft Annual rainfall: 7"
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