Portland, which has one of the country’s highest sewer rates, is prepared to spend a little more than $1 million collected from customers’ sewer bills to get homeowners to plant trees.

The initiative, which comes from the Bureau of Environmental Services, is known as a “treebate” program. And it’s designed to reduce stormwater runoff and improve local watershed health by increasing Portland’s living canopy.

If approved by City Council on Wednesday, Nov. 4, the program will give ratepayers a one-time discount of up to $50 off their sewer bills for each native tree they plant in their yard.

With a 10-tree limit, that could mean $500 in savings for the typical homeowner, who pays on average $596 a year for sewer and stormwater services in Portland. That average is the highest among six similarly sized U.S. cities like Denver and Sacramento, according to a 2008 city audit.

Portland is following the treebate lead of cities such as Washington, D.C., Austin, Sacramento and Seattle.

“It’s available to any resident,” says Dan Vizzini, a BES project manager. “We’re not targeting any one part of town. We want to see that canopy all over.”

The program has wrinkles. Gains for tree-loving ratepayers, for example, will be subsidized by those who choose not to plant trees. This matters even if you’re a renter, because landlords pass on their utility costs in the rent they charge.

But Paulette Rossi, a former longtime member of the Portland Utility Review Board, says the program will save all ratepayers in the long term. By limiting stormwater runoff, Portland reduces its dependence on building new concrete infrastructure to handle the downpours.

About 26 percent of Portland is covered with trees, according to city officials. They’re hoping to increase that to 33 percent in less than five years. The goal is to get 30,000 trees planted in Portland yards by 2013.

(Trees divert rainwater from sewers by soaking it up through their roots. They also provide shade and wildlife habitat in neighborhoods.)

This year, BES raised sewer rates by almost 6 percent, mostly to pay for increased capacity as part of the “Big Pipe” project to protect the Willamette River from sewage overflows.

Treebate funds were included for the first time in the bureau’s 2009-2010 budget. But the idea goes back to 2007 when the city’s so-called Grey-to-Green project began. Portland’s treebates are part of that project, which includes efforts to increase “ecoroofs,” decrease growth of invasive plants, protect homes from flooding by buying land in wetlands and build new “green streets”—roadways that allow rainwater to seep into the ground rather than stormwater drains.

Nearly 20 billion gallons of stormwater flows directly into Portland’s watershed each year. One tree with a 30-foot canopy can stop 700 gallons of rain from entering the sewers annually, the city says.

There is a limit on how many people can receive “treebates.”

And not every tree available for purchase is eligible for a subsidy. Invasive plants like the black locust are verboten. But Portlanders who plant non-native trees can get back 50 percent of the cost of the tree, up to $40 apiece. That figure increases to $50 for native trees like big leaf maples, Pacific dogwoods or Oregon crabapples. To participate, homeowners must produce a receipt to prove they bought the plant and agree to care for it for two years.

The watchdog Portland Utility Review Board approved the overall $350 million BES 2009-10 budget. However, Rossi notes that the treebate program comes just as the city is also considering a fee on garbage bills to pay for leaf pickup.

“It’s totally ironic,” Rossi says. “Here we are telling people to plant a tree to have more leaves to clean up.”