The news is shocking enough to render a weeping fig inconsolable.
Despite their reputation as indoor pollution busters, new research has confirmed that, when it comes to purifying our fug-laden homes, houseplants are useless.
Unless you transform your living room into Tarzan's lair, that is. Only then will you experience the clean-breathing benefits that have long been associated with ferns, palms and spider plants.
For, says Michael Waring, a professor of architectural and environmental engineering at Drexel University in Philadelphia, you need somewhere between ten and 1,000 plants — depending on the size and species — per square metre to achieve just the same 'air cleaning' effect as opening a few windows.
This will, of course, be a tragic development for millennials, whose fervent hoovering up of houseplants has sparked a potted plant boom unprecedented since the Seventies.
Despite their reputation as indoor pollution busters, new research has confirmed that, when it comes to purifying our fug-laden homes, houseplants are useless
Sold the lie that houseplants are both stylish (really?) and good for the environment (oh come on!), millennials now buy more cheese plants, aloe veras, bamboos and the like than any other generation, accounting for a third of all sales.
Typically for selfie-obsessed 20-somethings, the houseplant resurgence has little to do with green fingers and far more to do with provoking 'green envy' online.
Clean eating was so 2018. Today's Instagrammers are now into 'clean breathing', with the hashtag 'houseplants' bringing up more than 2.5 million posts on the photo-sharing app.
Even that much lampooned hippy standard of the Seventies indoor-jungle look, the rubber plant, is bouncing back. Rattan baskets and hanging planters are also in vogue again. The macramé army has returned — but is it here to stay?
Professor Waring, drawing upon 30 years of research, isn't so sure. Indeed, he maintains that plants are simply too slow at filtering out common airborne toxins known as volatile organic compounds (VOCs) such as benzene.
Released into the atmosphere after burning wood, coal and gasoline, these chemical compounds can cause eye, nose and throat irritation, frequent headaches and lung cancer.
In other words, not filtering them out is a pretty big flaw.
Professor Waring puts the blame for millennials' misplaced potted plant dependence on a rather unlikely organisation: Nasa.
In the Eighties, Nasa engineers were determined to find out how