Maria Gonzalez, who lives in New Haven, Conn., was envious of the other side of her street. It was lined with trees, offering some beauty as well as a shield from this summer’s unusual heat. But the sidewalk directly in front of her residence was bare, with trash littering patches of grass.

Then she met her neighbor Ed Rodriguez, an 82-year-old tree evangelist on a mission to fill the neighborhood with trees. Ms. Gonzalez was a willing convert.

This month, Mr. Rodriguez planted a crab apple tree in front of her home — his 90th tree in 13 years.

“I love to dig and mess around in the soil,” said Mr. Rodriguez who grew up in Puerto Rico, where he said he was surrounded by trees. He moved to the New Haven neighborhood in the 1960s.

As the United States sweats through another unbearable summer of record-breaking heat, planting more trees has emerged as a practical solution to cooling cities, especially areas known as “heat islands” where concrete and congestion magnify already brutal temperatures.

Yet filling a neighborhood with trees is not as simple as it seems. Funding and maintenance are issues for cities grappling with crime and housing. And not everyone, it turns out, wants a tree.

Mr. Rodriguez, who volunteers with the Urban Resources Initiative, a nonprofit partnered with Yale University, spends much of his time persuading his neighbors that trees are worth the trouble. Because the trees are planted by a volunteer organization, residents have to take some responsibility for making sure the trees survive and thrive.

The city of New Haven pays for tree planting and maintenance through a contract with the Urban Resources Initiative. Residents are responsible for watering the trees for the first five years.

He said that renters, who make up a large portion of his neighborhood, often thought they did not have the right to plant one. And some people don’t want to deal with maintenance or the nuisance of raking up leaves.

One neighbor whom Mr. Rodriguez talked to feared a shade tree would attract people who might see it as a spot for using drugs. Others wondered why the focus was on trees when their neighborhood had other issues.

“I try to convince them that the purpose and the outcome of having trees is greater” than the downsides, he said. He makes his pitch that trees filter the air, provide shade and enhance the property — and the butterflies are a plus, he added.

Urban forests — the forests and green spaces in cities and towns — have, on average, temperatures that are 2.9 degrees Fahrenheit lower than unforested urban areas, according to the Environmental Protection Agency.

Urban Resources Initiative volunteers said it was important for people to be able to pick their own trees from about 60 species.

“They’re the ones who are taking care of the tree by watering it every week, and so it becomes part of their family,” said Miche Palmer, a manager for the GreenSkills program, which is one of the Urban Resources Initiative’s efforts.

Urban Resources Initiative workers will check on a tree one, two and five years after it is planted. After the last benchmark, if everything is going well, the tree “graduates” and no longer is checked on by staff.

The program has planted nearly 11,000 trees in New Haven since 1995, with an average survival rate of more than 90 percent, managers said. It can take about 10 years for trees to provide shade, depending on the species. The trees the Urban Resources Initiative plants are usually around seven years old.

“It might not be exactly how folks thought relief would come, but if we talk about the long game, we could see these trees bring more than just cooling of temperatures, but it has all of these other benefits that could flow to communities,” said Beattra Wilson, assistant director of Urban and Community Forestry, a part of the U.S. Forest Service that helps fund tree-planting efforts around the country.

Mr. Rodriguez, who retired in 2006 after working for 35 years at the Yale New Haven Hospital including a Spanish and English interpreter, tries to make every tree planting a neighborhood event.

Mr. Rodriguez knows heat and a lack of trees aren’t the only issues his community is facing — there is noise from cars, litter and high taxes. But to him, trees are more than just shade and beauty. They are symbols of what is possible, important steps in the right direction.

“We need them for the beauty and all the benefits,” he said.

Earlier in August, student volunteers from Yale joined him to plant his 90th tree, and neighbors gathered around to watch. Once the crab apple was firmly embedded in the soil outside Ms. Gonzalez’s home, Mr. Rodriguez flagged down an ice cream truck and bought treats for the crowd.