Gardening in Extremes: How to Cultivate a Drought-Tolerant Landscape

One of the many, many plagues of this biblical era in which we live is drought.

Though some regions are more drought-prone than others, climate change is making dry conditions more widespread and more severe. A recent study in the scientific journal Nature found that drought has intensified in most parts of the world since the 1980s, which researchers attributed to a hotter, thirstier atmosphere. And drought is often just one of a buffet of wild extremes, as many areas seesaw between periods of deluge and stretches of unusually hot and dry weather.

Obviously, the choices you make in your raised bed will not, on their own, fix climate change. But one of the things that I like about gardening is the way it takes us into direct contact with problems, and strategies for dealing with them, and the physical planet. It’s a way to understand, in a tactile way, what the landscape is going through, and what it needs.

Water deeply, infrequently, and strategically

Plants are always responding to their environment. In a garden, that includes you. Their roots will stretch toward a water source, wherever that may be. And if you’re sprinkling your raised bed with water for a few seconds every day, you’re encouraging them to depend on your hose.

"Always water down to where the roots extend," instructs Yvonne Savio, the retired coordinator of the UC Master Gardener program in Los Angeles and author of gardeninginla.net.

That might be six inches for a lettuce plant, or a couple feet for a tomato plant. (Check here to see a chart.) Group plants with similar root depths and water needs together, so you can water more efficiently. By encouraging plant roots down into the cooler, moister part of the soil, they’re less likely to get cooked than if their roots were hanging out at the surface.

Savio suggests getting a moisture meter. Water your garden bed for a set amount of time—say, 15 minutes—and then check the meter the next day to see how far down the water went. If it only soaked four inches and your plant’s roots reach a foot, you’ll need to water longer. Instead of standing over your garden with a hose, consider a soaker hose that delivers water evenly across the bed.

Watering this deeply means you can water less often. Frequency depends on a lot of factors, from your soil type and the plant’s drought tolerance to the time of year, where you live, and how much it’s raining. But Savio’s estimates for veggie beds range between about once a week and once a month. Native plants and trees that evolved in your region usually need little or no supplemental water once established, unless they’re stuck in a pot or small street tree bed.

"I like to prioritize water use for where the clients are going to be hanging out the most," says Holly Kuljian, principal and landscape architect at Pine House Edible Gardens. "We do edible landscaping," she adds, and fruit trees and vegetables are typically thirstier. While drip irrigation helps save water, "we can’t design our gardens to be fully without irrigation. But we have to use smart practices." That means putting thirstier crops and colorful flowers closer to outdoor living spaces that clients use most, and planting tougher, low-water species elsewhere.

Among her favorite drought-tolerant choices: salvias, yarrow, agaves, prickly pear cactus, and lower-water fruit trees like pomegranate, apricot, and fig. And one of the simplest ways to save water, she notes, is to reduce or replace the lawn.

Plant wisely, and remember to mulch

Plants have evolved a variety of strategies over the millennia to avoid dehydration. Cacti and succulents, for example, are able to store water in the fleshy tissue of their leaves and stems; in exchange, they’re not able to perform photosynthesis very quickly.

"Their strategy is basically: Hold on and wait, and conserve resources," explains Rose Marks, an assistant professor of plant biology at the University of Illinois.

Some drought-tolerant plants have special compounds that allow cells to "fold up like an accordion" to survive dehydration. Other plants have leaves that can roll up in the sun to cool off. And some species, like yarrow, rosemary, and little bluestem, have small or narrow leaves that reduce water loss. "A lot of grasses are super water-efficient," notes Marks, "and they can be really beautiful and ornamental in a garden."

Often, you’re planting for multiple extremes. "For Oakland and the Bay Area, it’s really about flexibility, and designing for a definite future of drought but also really heavy rain," says Kuljian.

Beyond selecting plants with drought-tolerant characteristics, it’s always important to choose plants that are a good fit for your soil type, sun exposure, and climate—the classic "right plant, right place" principle of landscape design. This can involve some trial and error.

"The quest for the right plant, as we go through shifting climate conditions, is sort of ever-present," says Rashid Poulson, head of horticulture at Brooklyn Bridge Park in New York City.

In addition to facing recent episodes of unusually dry weather, the sun-drenched park has lean and sandy soils, which were installed on piers with limited load-bearing capacity. "I like to think of the park as a more extensive green roof," says Poulson. "We can run into instances where soils will dry out quite rapidly, even overnight."

Drought-tolerant native plants like switchgrass, little bluestem, and eastern red columbine have all worked well in these conditions, as well as various sedge species. Antennaria neglecta, also called field pussytoes, "has been really fun for some of our rockier and drier conditions," Poulson adds.

When it comes to edible plants, try to choose heirloom seeds and crops that are adapted to your area, says Dena Cowan, the curator of collections at Mission Garden in Tucson, Arizona, an agricultural heritage museum on the ancestral lands of the Tohono O’odham Nation that explores over 4,000 years of farming in the Tucson Basin.

"People say, ‘Well, it’s an heirloom tomato,’ but if it’s adapted to Chicago, and you’re planting it in the Sonoran Desert, it might not do well," Cowan notes. Mulch is also crucial in times of heat and drought, she says, to protect plant roots and keep moisture from evaporating.

Joining plots like the Agave Garden, the O’odham Gardens, and the Yoemi/Yaqui Garden, Mission Garden’s new Tomorrow’s Garden will explore the future of farming in the region, using agroforestry techniques to shade crops and incorporating semidomesticated native plants, including various species of agave, prickly pear, mesquite, and cholla.

"We’re drawing on traditional knowledge that people in this region have been using for centuries, or in some cases thousands of years," says Cowan. They’re also growing drought- and heat-tolerant crops that aren’t traditionally from North America, like jujube, carob, date palms, and cowpeas.

In reality, "the whole garden is a Tomorrow’s Garden," adds Cowan. In a hotter, drier world, "we’re experimenting with what is surviving."

Related Reading:

Gardening in Extremes: How to Tend Landscapes That Flood

How to Plant a Garden That Looks Good Year-Round