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How green is your garden?

Plant local. Collect rainwater. Let your lawn grow. A few simple steps can make your yard more energy efficient and save you money.

Many gardeners are moving away from chemical treatments for their lawns toward more eco-friendly methods that need less watering and mowing. Many gardeners are moving away from chemical treatments for their lawns toward more eco-friendly methods that need less watering and mowing. (Paul Giamou/Istockphoto)
By Carol Stocker
Globe Correspondent / March 25, 2010

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All gardens are green, right? As in, ecologically sensitive? Turns out, some gardens are greener than others. There are, of course, the obvious offenders — chemically treated lawns and their polluting run-off. But gardeners determined to create eco-smart yards should consider an array of ecological impacts, knowing that the right landscape strategies can make a garden energy efficient and save money.

The right vegetation can help keep a house cool during the sultry summer months and shield it from freezing winds in the winter. Native plants help support local ecosystems. Even something as simple as stone harvested from New England quarries can reduce a garden’s carbon footprint if it’s used instead of materials shipped from overseas.

“Our customers are getting much more excited about eco-friendly stuff and the new technologies than they were five years ago,’’ said Amy Van Doren, of Mahoney’s Garden Centers. For the Boston Flower & Garden Show, taking place through Sunday at Seaport World Trade Center, Van Doren designed an energy-saving “green roof,’’ that is, a roof that covered with a tapestry of sedums that functions as a natural and eco-friendly insulation.

While such new technologies are intriguing, many of the “greenest’’ garden ideas are the most basic, such as using plants that will thrive in the soil and location where you live. Environmentally conscious foodies live by the mantra “eat local.’’ Smart gardeners, meanwhile, plant local.

“You’ve got to know the site so you can create plantings that are low maintenance,’’ said landscape design/builder Tom Strangfeld, who will speak at the flower show tomorrow at 5 p.m. “My own yard on the Cape requires only eight hours of maintenance a year.’’

Strangfeld planted native, drought-resistant high bush and low bush blueberry, clethra, and inkberry in the dry, sandy soil and only had to water them their first two years until they were established. Where Strangfeld found unexpected pockets of water-retentive clay soil, he planted native swamp maples.

New England native plants do “a better job of supporting birds, bees, and butterflies than plants from other regions or countries,’’ said Shelburne-based landscape architect Sue Reed, author of the new book, “Energy-Wise Landscape Design.’’

Smart watering also saves energy. Using rain water in the garden saves taxpayers the expense of treating and transporting water that would go to sprinklers. There is much more interest now in irrigating with roof run-off collected in rain barrels. The Mahoney flower show exhibit includes a re-circulating water feature that is theoretically fed by rainwater from the gutters of a roof.

It also saves energy to use and keep as much material as you can on site, advised ecological landscape designer Risa Edelstein of Arlington. Instead of bringing in soil amendments, Edelstein makes her own by composting yard debris and food waste. She makes her own mulch from fallen leaves that get minced in the mower.

“It makes no sense to have my leaves hauled away in the fall,’’ she said, “and then buy mulch in the spring.’’

For those things you have to buy, stay local, Edelstein adds.

“For example, when you put in patios and walkways, use stone from New England instead of China or India,’’ she said. “Buy plants that were grown locally because you will save money on their transportation. Asking your nursery where their plants were grown tells them you are interested.’’

Farmers who lived without modern systems knew that planting strategies could help keep a home warm in the winter and cool in the summer. That’s why they planted evergreen winter windbreaks to the north of their homes and tall deciduous summer shade trees on the other sides.

Those rules haven’t changed. Plant, don’t pave, if you want to save money on air conditioning. “The more vegetation around your house, the cooler it will be in the summer,’’ said Reed. “To lower energy bills, reduce paving on the south and west side of your house, where summer heat accumulates. Where you must pave, choose surfaces that allow rain water to sink through and cool the soil underneath and use lighter colors that reflect more heat than darker colors.’’

She likes granite block, pre-cast concrete pavers, light colored bricks, compacted sandy gravel, crushed seashells, and loose pea stone.

Mahoney’s flower show exhibit features a patio surface of light tan 5/8th-inch pea stone because it is water permeable. “But I also love it,’’ said Van Doren, “because it makes leveling wobbly patio furniture a breeze. The truth is our customers worry about the potential mess of fall leaves on gravel, but honestly, the gravel will fall through the tines of the rake, so it is easy. The only caveat is that you need to edge it or that gravel will go everywhere.’’

Deciduous trees (which lose their leaves in the winter) will provide summer shade but let in winter light. Trees on the southeast or southwest side of the house will cast longer shadows than a tree planted square on the south side of the house, which would have to have branches that reach over the roof to cast shade, Reed points out.

“That’s because the noon sun casts the shortest shadows.’’ She added that “erecting any kind of overhang more than a couple of feet deep along the south side of a house will help cool it.’’ This is why you see photos of vine draped low long porches on the south sides of antique farmhouses.

Finally, you can’t talk about saving energy without talking about lawns.

“The lawn is the biggest cause of wasted energy in the garden,’’ said Penny Lewis. She’s director of the Ecological Landscape Association, which will present the first Environmental Vision Award to the flower show exhibit which best demonstrates ecological concepts.

Her advice: Don’t baby it.

Consider suspending summer watering. In nature, grasses green up with spring and fall rains, but go dormant in summer.

“There are people who have no problem with their lawn going dormant in the high heat. It will come back in the fall if the soil is healthy and the grass roots are deep, and may even stay green during the summer with minimal water,’’ said Frank Koll of Greenscapes Lawn & Garden Services in Arlington.

Grow less lawn and mow it high, Koll advised.

“As a company we try to reduce the amount of turf. You don’t want to grow grass where it shouldn’t be grown, like in shade or where water collects.’’

The Trustees of Reservations, based here in Massachusetts, is reducing the amount of manicured lawns at its holdings by 50 percent.

Chemical-dependent lawn care is becoming increasingly controversial. “Feed the soil, not the plant,’’ is a popular eco-gardening motto. We now understand that living soil is home to billions of beneficial organisms that help plants grow and fight off diseases. Chemicals can kill these micro-organisms, resulting in “dead’’ soil, and plants dependent on chemicals for life support.

“You can also reduce mowing by growing drought tolerant disease resistant grass seed mixes such as Ecoblend, Pennington’s Smart Seed, or Pearls Premium, which are intended to be maintained at four inches or higher,’’ said Koll. “Sometimes you only need to mow once or twice a season.’’

Mowing once or twice a season? That may be the smartest garden move of all.