A curtain of vines

Thinking about ways to reduce our energy use for cooling next summer, I hit on the idea of shading some west-facing windows at the back of the house with foliage. I don’t want to block the three full-length windows that provide our main view of the garden. But a pair of windows near the southwest corner could use some summer shade. Vines could be just the thing.

These windows get a lot of afternoon sun in summer

    The Department of Energy explains that vines can lower the temperature of a house in three ways. In the process of evapotranspiration, plants actively transport water, and when it evaporates, it cools the surrounding air. Shade reduces solar gain, of course, and vines can blanket the side of the house, creating an insulating air space. Put together, these contributions can reduce temperature shifts by 50 percent.

Vines can keep a house cool-photo Michael Palmer

    I’m not proposing to cover the whole west side of the house in vines yet. My idea is to start with a large container of fast-growing vines to keep the sun off that pair of windows.

    When I put up supports, I’d like to leave space between the vines and the house to permit air flow. I’m picturing a wooden frame attached to the siding that would hold some lattice or wire fencing to support the vines. Maybe I can attach hinges at the bottom of the frame so I can swing it down when it comes time to paint the house again.

Lattice attached closely to the garage wall leaves little air space behind it

    I’ve learned a lesson from a large wooden planter I placed directly on the ground in a shady corner. Tree roots grew up into the potting mix, making it hard to remove and replace old growing medium in the spring. This time I’ll prevent that by standing the planter’s corners on bricks to leave an air space that the roots can’t jump.

    Next will come the fun part: choosing which vines to grow. I could go with classic fast-growing flowering climbers such morning glory (Ipomoea purpurea), moonflower (Ipomoea alba), or mandevilla (Mandevilla spp.). These all originate in Central America. I could choose edible options: scarlet runner beans, cucumbers or squash. 

Morning glories are lovely and grow fast

    But I'd prefer to use native vines. I’ve already got two trumpet honeysuckles (Lonicera sempervirens), a cross-vine (Bignonia capreolata), and a trumpet vine (Campsis radicans) close enough to the proposed site that I’d like to try something different.

Trumpet honeysuckle is going strong in a dry spot against the house

    Last summer I grew a blue passionflower (Passiflora caerulea) vine in a container on the deck, wrapping its long stems around a black metal obelisk stuck in the pot. That one’s from South America. There’s a native cousin called maypop (Passiflora incarnata) that looks pretty. It’s reportedly a woody vine in the Southeast that dies to the ground in colder areas, which would serve my purpose. Growing it in a planter would curb its tendency to aggressive root spread.

Maypop, a native passionflower-photo H. Zell

    Another native possibility is woodbine (Clematis virginiana), a vigorous grower with white flowers August to October that could accept cutting back in winter. A quick search uncovers warnings about its spreading by seed, though, so maybe not.
   

Climate action in the garden

It’s been a discouraging month of environmental news. The UN climate summit confirmed that there’s not a lot of time left for international action to prevent catastrophic climate change, but national governments, notably ours, are not making adequate commitments. 

Unlike polar bears, we humans do have the power to combat climate change-photo Gerard van der Leun

A group of ornithological organizations published a study estimating that we’ve lost 3 billion birds--29 percent of the bird population of the US and Canada--since 1970. Leading causes cited included habitat loss and widespread use of pesticides. The Audubon Society reported that by 2080, 389 out of 604 North American bird species will find most of their current ranges unlivable if the climate remains on track to rise by 3 degrees Celsius.

No more loons on US lakes unless we clean up our act-photo Bert de Tilly

    While our national leaders are dragging their feet, what can we gardeners do to address climate change? Collectively our gardening choices can make a real difference. We can do our part by holding carbon in soil and plants, planting strategically to reduce our homes’ energy needs, and choosing materials with less embedded carbon cost.

    You’ve undoubtedly heard that saving trees—for example not burning down the Amazon rainforest or clearcutting Forest Service land in the Northwest—can help combat climate change. The same principle operates in our backyards. Trees hold carbon and keep it out of the atmosphere for as long as they live. Perennial plants also contribute.

Big trees sequester lots of carbon-photo ukgardenphotos

    But you don’t have to hem in your yard with big trees. We can also help by following Earth-friendly gardening practices. Soil sequesters carbon, and the more organic material you add to it, the more carbon it will hold. That means keeping fallen leaves on your property makes even more sense. 

It's not waste, it's precious organic material

    If you’re planting a sizable tree, you can help even more by positioning it to reduce your energy use for heating and air conditioning. Deciduous trees shading the house in summer can provide substantial cooling, and in winter when leaves are down, they allow warming sunshine through. Evergreens that block winter winds can reduce energy needs too.

Trees shading the house save energy-photo American Society of Landscape Architects

    When we’re shopping for materials to use in the garden, we have a chance to avoid high embedded carbon costs. For example, did you know that those little white pellets of lightweight perlite that you see in bagged potting mix come to us from the Greek island of Milos, where volcanic glass is mined and heated to 1600 degrees Fahrenheit to puff like Rice Krispies? Meanwhile, stripping peat bogs for the peat moss in that commercial potting mix releases carbon into the atmosphere and eliminates the carbon sink they provided. 

Mer Bleue peat bog, Ontario

    Instead of buying bags of this environmentally costly stuff, you can make your own potting medium at home. Or you can choose Organic Mechanics potting mix, which is made from compost and coconut fiber, or coir.

Making peat-free potting mix at home

    If you’d like scientifically informed straight talk on how to make shrewd gardening choices that will help combat global warming, check out The Climate Conscious Gardener, published by Brooklyn Botanic Garden.

Sign for the April 2017 Climate March in Washington, DC