Solution
The answer is marsh mallow. Did you know that marshmallows (the candy) were originally made from the roots of this plant? History of the marshmallow
In creating this puzzle, I sought photos of each mallow species in the setting it's named after. Alas, though I grow Venice mallow in my garden, I could not find any pictures of Venice mallow growing in Venice.
Congratulations to yesterday's solvers Anna K., Anna J., Darwin, Bridget, Kalpana, Summer, Jessica, Jacob C., Maddy, Peter M., Trent, Ena, Dr. Yetman, Mrs. Gregg, Graham, and Kate. Thanks to everybody who made a guess!
Though he now teaches mathematics, Dr. (né Mr.) Shapiro's first job in a K–12 school was as a lunch monitor in Davis, CA. It was there that he originated the Puzzle of the Day, even rewarding correct answers with tickets in denominations like "15 points" (though without a clear idea of how he'd ultimately redeem these). Dr. Shapiro's favorite puzzle from this pre-professional era was "Tell me the location of the beehive on this campus."
Ten years later, Dr. Shapiro revived Puzzle of the Day at Proof School, writing each day's puzzle on a name tag. After 600 puzzles or so, he was just starting to feel normal about students reading his chest all the time when campus closed and the puzzle, like the rest of our lives, moved online. New puzzles are posted daily on school days.
Want to catch up on old PotDs? There's an archive currently containing puzzles from March 2020 to March 2021.