REAL ESTATE’S time-honored mantra—location, location, location—may need a fresh garnish: vegetation, vegetation, vegetation.

Earlier this year, Reed College economist Noelwah Netusil unveiled the first-ever study combining three Portland obsessions: home prices, walkable neighborhoods, and plants. Netusil confirmed that home prices rise when new amenities—stores, restaurants, mass-transit stops—open within walking distance. So far, so obvious in a city that planners envision as a collage of dense urban villages. But she also found that those price increases are greater in neighborhoods thick with trees, parks, lawns, and other greenery—and it’s not just a little boost, but a big one.

In an analysis of two years of Portland home sales starting in 2005, Netusil compared prices with walkability scores from the City of Portland and a 2007 Metro survey of land cover. Here’s an example of what she found:

Say House A and House B are both worth $300,000, the average price in Netusil’s data set. House A sits in a concrete jungle, House B in a verdant, tree-lined ’hood. New grocery stores open within half a mile of each. Both owners are happy—as they should be. (Portland Monthly’s April real estate survey found that the average homes in some of Portland’s most walkable neighborhoods actually increased in value during the real estate slump.) But House B is a happier home by far. According to Netusil, the new store adds just $3,500 to the potential price of House A; in House B’s leafy Eden, the improved walkability score sprouts $22,000 in greater value.

While Netusil’s study (funded by grants from the National Science Foundation and Reed College and presented at a Portland State University seminar in January) seems like a smartphone app waiting to happen, it doesn’t explain why greenery acts as such a force-multiplier for walkability. It does suggest that Portland’s official pursuit of more sylvan neighborhoods—like the city’s $50 million Grey to Green initiative, which has planted more than 11,000 new trees since 2008—might help the housing market as well as stormwater management, the program’s raison d’être.

Whatever the larger implications, in this tough real estate market Netusil’s study should inspire some would-be sellers to invest in mulch and gardening gloves—especially if they can walk to the nearest gardening store …