“Landscape as drug is our concept,” says Brent Bucknum, the founding principal of Oakland, California’s Hyphae Design Laboratory. It’s his way of explaining how he and his team, which includes ecologists, engineers, and landscape architects, got involved in one of the most unusual clinical trials in modern medicine. Known as the Green Heart Project, a collaboration among Hyphae Design Lab, the Nature Conservancy, and the University of Louisville's Christina Lee Brown Envirome Institute, the study is a controlled clinical trial that will evaluate the health effects not of a new pharmaceutical product, but of trees.

Specifically, researchers are testing the effect of urban vegetation on cardiovascular health, measured by the stiffness of participants’ arteries, which correlates to higher rates of heart disease – one of the leading causes of death in the United States. After baseline data is collected on the trial’s 700 participants, one group will be “treated” with a sudden bloom of greenness in their neighborhoods–new street trees, shrubs in people’s front yards, buffer plants along freeways. A control group will not receive additional greenery. After three years, researchers will compare the health of the two groups. “What we are expecting to see is less [change in stiffness of] the arteries of the people living in the greener areas,” says Aruni Bhatnagar, the director of the Envirome Institute.