Which fruits and vegetables are best to plant for the environment

(Illustration by Emily Sabens/The Washington Post; iStock)
11 min

Venture into my backyard and you’ll see a kale patch, a riotous row of Cascadia snap peas and some straggly tomatoes that, except for one banner August, succumb each year to San Francisco’s foggy summers.

My vegetable patch is a produce factory. Every week, I can pick a hearty salad and as much oregano and thyme as I like. Except for the tomatoes, which I refuse to give up, these crops were selected by what my family would eat and what nature dictates will grow on my little spot on the planet.

As a climate columnist, I wondered: Could I make better gardening choices for the climate? More importantly, does it even matter?

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Industrial agriculture produces an unprecedented amount of food. We can grow roughly five times more grain per acre today than a few centuries ago. Whereas growing a bushel of wheat once required laborers to work in fields for hours, modern farmers can do the equivalent in minutes.

Fossil fuels make it possible. They power our tractors, fertilize our crops and supply herbicides or pesticides that kill weeds and bugs. If we are what we eat, we are, at least a little, composed of fossil fuels.

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But this has come at an enormous environmental cost. By adding 90 times more energy per hectare to the food system compared to pre-industrial times, agriculture contributes about 25 percent of the world’s greenhouse gas emissions. It has also converted vast swaths of wilderness into rows of monoculture crops and left massive marine dead zones in places like the Gulf of Mexico because of fertilizer runoff.

So I wanted to find out: Could my garden, fed by compost and drip-irrigated, beat America’s agricultural behemoth on the climate front?

Rethinking Big Ag

One alternative to industrial farming is regenerative agriculture. No strict definition exists, but this way of growing food emulates nature by building the fertility of the soil, usually by applying more compost and manure, rather than synthetic fertilizers, and avoiding plowing. While productivity per acre may not always rival their conventional counterparts, these farms are often more resilient and far easier on the environment.

Pick up a handful of soil in fields of monoculture soy, corn or wheat, and it sifts through your fingers, largely stripped of organic matter and nutrients. Only successive rounds of fertilizer, herbicides and pesticides maintain its impressive productivity.

On regenerative farms, the rich and crumbly black soil is held together by a mix of organic matter, nutrients and microorganisms, researchers say. This healthier soil, in turn, enables plants to grow better with less irrigation, fertilizer and fossil fuels. There’s no bright line dividing the two. Plenty of small, regenerative farmers use fossil fuels, while big growers are practicing no-till farming to build up solid carbon.

We’re just starting to learn where it makes sense to go big, and where we should grow locally.

When it makes sense to grow at home

Tiffanie Stone, a researcher at Iowa State University, has done one of most comprehensive life-cycle analyses of growing crops at different scales, from seed to farm to plate. Her team, publishing in the peer-reviewed journal Science of The Total Environment, examined small-, medium- and large-scale farming from gardens to massive farms near Des Moines in the heart of America’s highly productive farmland.

In theory, the state could feed itself many times over. In reality, 90 percent of the food is shipped from beyond its borders. It’s a perfect place to examine the relative advantages of small vs. big agriculture.

Stone and her co-authors measured four environmental effects — global warming potential, fossil energy consumption, water use and land use — from farming in the region. By looking at each one, at different scales, they could answer whether it made sense from an environmental point of view to grow a head of lettuce and other produce closer to home, or ship them 1,600 miles from California.

In most climate calculations, food miles don’t matter too much. Food’s carbon footprint tends to come from growing, processing, storage and disposal, not transportation, which contributes around 10 percent of the total on average. So whether you grow it next door or on the other side of the country, the biggest difference for the climate is how it’s grown.

When Stone’s team looked deeply at the environmental effects of producing different categories of food, from protein to vegetables, in the Des Moines area, they found small growers weren’t as inefficient as many assumed. In fact, midscale commercial farms and even home gardens had much lower environmental impact overall.

In the Des Moines area, they found at least half of the region’s food could be grown locally with lower emissions, energy and water compared to large factory farms — if not always cheaper.

Then they went one step further. They ranked the environmental impact of 18 vegetables grown in the area based on emissions and water use as part of a second study. A few crops offered the most environmental bang for the buck at the small scale: lettuce, carrots, onions, tomatoes and others (see chart).

Small farms didn’t perform quite as well compared to Big Ag on crops such as potatoes and pumpkins that store well or lend themselves to mechanized agriculture. But all vegetables grown on larger farms in the study consumed more water and energy compared to those on smaller farms.

Does this mean all Iowans — and all of us — should grow their own lettuce? Maybe not. Not every state is blessed with such fertile soil. The state’s agriculture is also highly seasonal. Temperatures in January average below 32 degrees Fahrenheit. And thanks to economies of scale, as well as farming and fuel subsidies, it can still be cheaper to grow some kinds of lettuce in a massive California field and truck it across five states.

Instead, Stone says, the results point the way to a much bigger role for small producers. Gardens and small farms can create a food system that’s more resilient, less wasteful and better for the climate and communities while complementing the massive productivity made possible by conventional agriculture.

We are only just starting to build out local food systems that do this in most places. After decades of focusing on size, it may take decades to rebuild the infrastructure and relationships to grow, distribute and sell produce closer to home.

“I have seen claims local is always better, but I haven’t found that evidence,” says Stone. “It depends on the context and the purpose. The pros are going to have higher yields. We’re not arguing that point. But there can be other benefits. Ideally, it is a balance between efficiency and resilience.”

Where growing locally comes up short

If the goal is to sequester carbon in the soil, I concluded there’s very little ordinary individuals can do with tiny backyard plots. Even on large farms, some researchers contend, relying on soils as a major, additional carbon sink may be “unrealistic.”

Even if every American had a garden, it would only displace a fraction of conventional agriculture. Just 2 percent of U.S. farmland is devoted to growing fresh fruits and vegetables. The majority of farmland grows commodity crops such as soy and corn, destined to be turned into livestock feed, biofuels or industrial ingredients such as high fructose corn syrup.

So I asked Alessandro Ossola, an agronomist at the University of California at Davis, whether growing my own kale and snap peas was meaningful or merely symbolic.

“The amount of carbon that you get in your garden bed is a tiny fraction of the emissions from your lifestyle,” he said. “But gardens are driving positive change through food and plant production in general. They are essentially helping communities adapt to our new future.”

While agriculture has never grown so much food, it has lost variety and resilience along the way. He pointed to a Tuscan painting from the 1600s in one of his studies showing 115 varieties of pears growing in that region. Today, the United States grows about 10 commercially.

If industrial farmers have spent the past century relentlessly focused on efficiency, he argues, the next century must also focus on resiliency. We are growing too much food, not too little, the majority of it for livestock, biofuel refineries and food manufacturers, rather than people’s tables. While industrial agriculture will supply most of our calories for the foreseeable future, it will pay to rediscover our relationship with healthier food and prepare for a more volatile climate future.

Small-scale farming is key. Ossola plans to bring more gardens and small-scale farming to urban food deserts, reseed heirloom varieties of crops and reconnect people with nature. He points to the Agriculture Department’s expanded urban agricultural program, and nonprofits like Fleet Farming in Orlando which turn private yards into gardens to feed the community, as new ways small-scale agriculture is returning to our cities.

“I see gardening as a way to reconnect us as humans with nature,” he says. “This can be done at a very small scale in your garden or even on your balcony. We need to reframe how we think of ourselves in the landscape.”

How to grow a climate-friendly garden

A nearly infinite set of resources on the internet and books promises to guide your gardening decisions. But most questions can only be answered by experience. Here are a few of the top tips from expert gardeners about how to get started.

  • Start with starts. Conditions have to be just right to sprout seeds and transplant them. If you’re planting for the first time, says Tamar Haspel, author of “To Boldly Grow” and a food columnist at The Washington Post, seedlings are easier. Once you know what will grow, you can turn to seeds. “Gardening, even more than politics, is local,” Haspel says.
  • Start small, at first. Too many gardeners start with grand ambitions, only to give up when their green dreams don’t materialize, says Emma Kriss of Green America, a nonprofit organization. Start small and steadily expand your domain. Plant just one raised bed, or use a small hydroponic kit or even a pot on the windowsill.
  • You can grow anywhere. Only have a window or a fire escape? Herbs are for you. Even tiny backyards support a surprising amount of produce. The square-foot gardening approach lets you maximize any area by planting in a grid instead of rows. The Farmer’s Almanac garden planner can help you tailor this to your climate, or just grab a piece of graph paper, some square-foot spacing measurements and the USDA plant hardiness growing zones.
  • Go perennial. Annual plants are a lot of work. Perennials require you to plant once while producing year after year. Try herbs like mint, a vegetable like asparagus or rhubarb, as well as fruit and nut trees or bushes such as blackberries, citrus and hazelnuts. Even if you lose interest, you will have a beautiful bush or tree, as well as a climate victory.
  • Make weeding and watering easy. “If there are two things people who have jobs don’t have time for,” says Erin Torgerson, a chef and farmer in Durham, N.C., “it’s weeding and watering.” To help, mulch will keep the soil moist, save you water and tamp down weeds. Automatic watering is also a lifesaver. Buy a timer, hook up a hose, install a drip irrigation line and your plants will thrive all summer long with only a fraction of the time, effort and water.
  • Don’t be afraid to plant for beauty. “Plant a small square of wheat,” Torgerson says. “It is beautiful. I also think corn is stunning. You’ll gain some appreciation for how it grows.” Even a 3-by-6-foot plot of wheat could give you enough for a sourdough loaf. It offers a tangible appreciation for what goes into your daily bread.
  • Expect failures the first time. “Everyone can grow something in their backyard,” Torgerson says. But your local climate dictates what you choose. When she was living in Steamboat Springs, Colo., the growing season was brief. But she planted crops from her hot-weather childhood in the South: okra and tomatoes. “There was no chance of those happening,” she says.

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