Absinthe Ingredient Makes The Roof Grow Greener

Green roofs are just the coolest thing. Literally – as one study noted, “the plants and growing medium of a green roof provide shade, thermal mass, and evaporative cooling that reduces temperatures on the roof surface and in the building interior below.”

These living roofs have other benefits, as well, including helpfully absorbing and slowing rainfall runoff. Plus, they just look great. And now there’s research out of the University of Greece that highlights how green roofs can help preserve local character and biodiversity in old Mediterranean cities by using a trio of native plant species – including one that’s a common ingredient in the spirit absinthe – along with the solids left behind from local winemaking.

green roofs

Not Athens, but a beautiful green roof in San Francisco at the California Academy of Sciences (image via Wikimedia Commons)

Now, by “old Mediterranean cities” we’re talking here about places that “lack areas that could be converted into conventional green spaces,” according to the researchers. So green roofs immediately gain attraction. “Green roofs are still relatively uncommon in Mediterranean countries,” researcher Maria Papafotiou said in a statement, “although these areas would significantly benefit from the ecological and technical functions of this technology.”

In their research, Papafotiou and her colleagues planted three Mediterranean aromatic xerophytes – these are species of plants that do well with little water – Artemisia absinthiumHelichrysum italicum, and H. orientale – on an Athens roof using a couple of different soil substrates, one of which included grape marc compost, the solids left behind after wine is pressed off the grapes. They also varied the depth of the soils and employed differing watering regimens.

All the plants did well, but the artemisia – a plant that contains a psychoactive compound, thujone, which gave absinthe its (undeserved) crazy-making reputation – did best, particularly when paired with the grape marc composting.

The researchers also noted what they term a “remarkable result” with water-saving implications: “shallow compost-amended substrate with sparse irrigation resulted in similar or even bigger plant growth of all plant species compared with deep peat-amended substrate with normal irrigation.”

The research was published in HortScience, and the abstract is available online here.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.