Roman Greenhouses

While musing about removing those greenhouses sitting over unexcavated parts of Herculaneum, I came across this surprising statement:

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Italy is one of the leading countries in protected cultivation on account of its mild climate in winter and the old Italic feeling for greenhouses which appeared first in the ancient Rome.

Furthermore https://www.actahort.org/books/481/481_96.htm says the focus now is on lucrative off or shoulder season fruits and veggies, so these are concentrated on Italy's mild coastlines and the south (even where summer heat shuts them down). The availability of cheap plastic films made things more affordable than glass. The Roman greenhouses are often misrepresented as using implausable glass roofs to grow off season cucumbers on Capri for Tiberius. But a very interesting source https://journals.ashs.org/hortsci/view/journals/hortsci/57/2/article-p236.xml explains:

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The origins of controlled-environment horticulture is the Roman specularia, which were wooden frames covered with transparent stone, a form of gypsum (selenite), known to the Romans as lapis specularia or transparent stone. The specularia was used for out-of-season culture of long-fruited melons, C. melo Flexuosus Group.

That is a truly fascinating illustrated article (actually, like the other, a book abstract), but I'm not sure why they speculate the greenhouses were near Villa Jovis when Tiberius had 4 other villas on the same island. Jovis is kind of a backbreaking climb, although maybe it pokes up into the sun on foggy days: