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Don’t sweat it, plant it: Trees boost overall health and cut cooling costs

Ask the Expert Gardening
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"Korean dogwood is always a favorite because it blooms for about three weeks and it has big, white flowers that usually fade to pink," landscape designer Jim Egan said. Adobe Stock

Some home improvements — a sleek new kitchen, a fresh coat of paint — have an instant visual impact that improves the value of your home and your life within it. Others, like a more efficient furnace or insulation retrofit, are less glamorous, but can lower your energy bills for years to come. Either type of project, of course, will generally set you back a bunch of money.

But there’s another improvement that can beautify your home, boost curb appeal, and lower your energy bills at the same time. And while it can still be costly, sometimes a squirrel will do the job for free.

Trees.

Often overlooked as a home improvement, trees can cool our homes on summer days, create natural play structures for our kids, and even improve our sense of well-being. While most homeowners surveyed by the National Association of Realtors report feeling greater enjoyment at home after completing a remodeling project, trees can improve not just our moods, but our actual health. The US Department of Agriculture calculated that, by removing more than 17 million metric tons of air pollution in 2010, America’s trees prevented 850 deaths and 670,000 incidents of acute respiratory symptoms in that year alone. Other research has linked nearby trees to reduced stress levels, lower crime rates (even after controlling for other factors), and faster recovery from surgery.

Studies also have shown that mature street trees increase property values — by up to $1,750 in Athens, Ga., and an average of $7,020 in Portland, Ore., the journal Landscape and Urban Planning reported in 1988 and 2008, respectfully. “There’s a big difference to buyers when you pull up to a property and there’s a beautiful ornamental tree or a very mature tree, maybe with a swing on it,’’ said Corey Morris, a real estate agent with the Level Up Group at Keller Williams Realty in Braintree. Buyers rarely specify upfront that they need a nice tree in the yard, Morris added, “but it is one of those things that I do believe would, as far as curb appeal is concerned, potentially push a buyer over the edge to make an offer on one home versus another one.’’

Easier to quantify is the way trees can lower the air temperature around them and lessen the load on a home’s cooling system in summer. “Neighborhood-wide tree canopy has been shown to lower overall air temperature,’’ said Mat Cahill, an urban forester with the Massachusetts Department of Conservation and Recreation and director of the state’s Greening the Gateway Cities program. A leafy canopy overhead saves homeowners energy and money and also reduces the urban heat island effect — that is, the extra heat absorbed and radiated by a city’s abundance of concrete and asphalt. That, in turn, helps with community health, Cahill added, lowering the rates of heat-related deaths, which are projected to double in Boston through the 2020s.

Casting shade and blocking solar radiation is a key part of their cooling power, but trees also pull water out of the ground and up into their leaves, where it evaporates in a process called evapotranspiration. “That evaporation kind of cools the ambient air temperature around the tree,’’ said Cahill, similar to sweat evaporating off your skin in a breeze. Put it all together, and a dense urban tree canopy can lower the surrounding air temperature by up to 10 degrees, according to a 2019 University of Wisconsin study.

Cahill recommends planting deciduous trees on the southeast and southwest sides of a home, where they can maximize summertime shading but shed their leaves to allow warming sunlight in winter. “We typically say to leave the southern exposure open to create a little sun pocket — it’s a valuable tool to help warm the building during our long New England winters,’’ he said. “In our climate, winter heating days exceed our summer cooling days by a wide margin.’’

Well-placed trees can help homeowners reclaim their outdoor spaces, said Jim Egan, a landscape designer with Land Design Associates in Norwood. “If you have a southwest- or south-facing patio, it can get brutally hot,’’ Egan said, and a strategically planted sugar maple or fast-growing tulip tree can provide shade in the hottest part of the day. “And then folks can sit out and enjoy the patio when normally they wouldn’t be able to.’’ In small yards, trees also make effective screens. “Essentially, they create green walls that provide privacy and buffers and sound absorption for street noise, and help enclose the space,’’ Egan said.

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Tulip trees are fast growers, according to landscape designer Jim Egan. —Adobe Stock

Color is another reason people add trees to their landscapes, whether for spring blooms or bright fall foliage. Red and sugar maples are obvious choices in New England, Egan said, and he likes the three-week bloom of a Korean dogwood. “One tree I love to use around patios and entryways is called a sweetbay magnolia,’’ Egan added, which appeals to multiple senses. “It’s a summer bloomer, and it has the most amazing fragrance later in the day.’’

There’s more to an ornamental tree than flowers and foliage, though. “Other trees have very nice bark, so they’ll provide textural interest,’’ Egan added. “A stewartia has beautiful, almost military camo bark that exfoliates as it gets older.’’ Keith Bernard, an arborist with Barrett Tree Service East, said he loves the paperbark maple for its similarly “beautiful exfoliating bark. It has fantastic fall color, but I happen to think it’s most striking in the winter when it’s out of leaf,’’ Bernard said.

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Stewartia trees are known for their almost Army camouflage-like bark. —Adobe Stock

When it comes to selecting a tree species, every arborist I spoke to said it’s about “the right tree in the right place.’’ No one tree is perfect for every home; indeed, a near monoculture of maple trees in Massachusetts is one of the biggest threats to our urban canopy, according to Rick Harper, extension associate professor of urban forestry at University of Massachusetts Amherst.

“Our state tree is the American elm tree … they’re kind of majestic looking, and they were planted everywhere — streets, parks, private landscapes,’’ Harper said. “And then Dutch Elm disease came through in the 1950s and ’60s and essentially killed all of our elm trees.’’ But we didn’t learn, Harper said. We replaced a lot of those elms with Norway maples — one in every two street trees in Massachusetts is now a maple — which are vulnerable to the Asian longhorn beetle.

In 2008, an infestation by the destructive pest forced officials to cut down more than 27,000 trees in Worcester, including most of the mature maples in the city’s Burncoat neighborhood. Devastating as it was, it allowed Harper’s colleagues a unique chance to compare summertime energy use in impacted areas before and after the trees were removed. They found energy use increased nearly 40 percent after correcting for weather variations.

That’s why Greening the Gateway cities has planted more than 26,000 trees in 14 Massachusetts cities. Homeowners in target neighborhoods can request a free tree on their property, but must sign an agreement to water the sapling for the first two years. “That’s absolutely critical for the plant’s survival,’’ Cahill said. “By doing that, we have a program-wide survival rate of 90 percent, which is almost double the national average of these types of tree-planting programs.’’

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The fragrant sweetbay magnolia. —Adobe Stock

Because trees are so thirsty, they can also help manage water issues, from basement seepage to flooded storm drains. “In wet areas, the classic sponge is a weeping willow,’’ Bernard said, but redwoods and tupelos can also tolerate flooding. “Those trees are pulling up enormous amounts of water. So if you have a low part of your yard, or you’re on the edge of a swamp or something, there are certainly trees that can reduce the water in your basement, because they’re pulling up hundreds of gallons a day.’’ Meanwhile, large trees ease the burden on storm drains and urban sewers by catching rainfall before it hits sidewalks and streets, reducing the risk of flooding.

Of course, unlike a new kitchen, it takes a while for a new tree to reach its potential, which can test either your patience or your pocketbook. “We can get any size plant you want,’’ Egan said, “however, the price goes up exponentially as you get bigger.’’ (Cahill said smaller trees retain more of their root systems during transplanting and will actually catch up to bigger ones.)

But — unlike a new kitchen — a tree gets more valuable with age. “The second you put in a road, it needs maintenance … whereas a tree is growing and providing more ecosystem services every year as that canopy gets bigger and bigger,’’ Cahill said.

And those early years pass more quickly than you might expect. After our daughter was born in the spring of 2012, I noticed a tiny oak sapling in our front yard, no doubt planted by a forgetful squirrel over the winter. Since it was “born’’ around the same time she was, I was compelled to let it grow — and it did, with our daughter affectionately referring to it as “her tree.’’

Eight years later, our daughter’s old enough to climb that red oak, and it’s now big enough to support her. It shades our yard and front porch from the brutal late afternoon sun, too. But just as important, it’s beautiful to see her love and care for this piece of nature, to see it grow each year right along with her. And to think that one day, when she’s much older, our daughter might drive by this old house and see that her little sapling sibling has become a grand, towering oak — and perhaps she’ll realize just how strong and graceful she’s become, too.

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The author’s daughter sits in her “sapling sibling.” —Jon Gorey

Sure, maybe I’m being overly sentimental about it. But I’m not alone. “When folks are moving out of a long-held home, it’s usually not the dishwasher, the dryer, the stove they cling to,’’ said Judy Alexander, a realtor with Barrett Sotheby’s International Realty in Lexington. “It’s the trees which are usually tied in with a family event.’’

Jon Gorey blogs about homes at HouseandHammer.com. Send comments to jongorey@gmail.com. Follow him on Twitter at @jongorey. Subscribe to our free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp.