What are San Marzano tomatoes, exactly? Chowhound foodieX2 recently encountered a can labeled "San Marzano," and underneath those words, in fine print, it read "style." A case of misleading marketing, or is there actually something called a San Marzano–style tomato?
Let's roll it back, says bob96. Italy's San Marzano region is a DOP (Denominazione d'Origine Protetta, which means "designation of protected origin"). It's a region with its own trademark, just like certain European wines and cheeses have. (It's also sometimes referred to as DOC, Denominazione di Origine Controllata.)
But San Marzano is also a variety that can be grown anywhere tomatoes thrive, and as long as they're not fraudulently marked DOP, GH1618 says, they're perfectly legit.
San Marzanos are a true heirloom variety, junescook notes, meaning they can be grown from seeds you harvest and save from year to year. They're high producers and significantly meatier than other tomatoes, with less juice and fewer seeds. While junescook grows them and prefers them to Romas for making sauce, pine time grew them and wasn't impressed (maybe something to do with the local alkaline soil in San Diego, pine time says). That's terroir for you.
Discuss: What exactly is San Marzano "style"?