If we’ve learned anything as food growers in recent decades, it’s that climate change has placed not just one but many kinds of stress on our gardens and farms. “Global warming” does not adequately describe the “new normal,” given that many food sheds and farms have suffered from a variety of catastrophic floods, freezes, droughts, wildfires, heat waves, grasshopper infestations and crop diseases over the past few years.
The big, paradoxical question confronting many farmers and gardeners is: How do we adapt to and plan for uncertainty? While such a question may initially seem unanswerable, farmers from all parts of the world have responded over many centuries through better crop selection and strategies to mitigate the worst effects of sun and wind.
To best adapt, we need thousands of different annual crop varieties evolving in fields and undergoing evaluation in continually changing climatic conditions, as well as responding to pressures from novel strains of diseases, garden pests and weeds. But just how do we determine and select which annual crops’ seeds are most likely to help us cope with the drought, heat waves, severe storms and other climatic disasters we face?
Learn From Desert Plants
As a Southwest gardener and orchardist already facing hot, dry conditions, I try to take tips from the native desert wildflowers growing around me. They’ve convinced me that there is more than one way to approach a drought. While most seed catalogs interchange the terms “drought tolerance” and “drought resistance,” these terms are often used imprecisely to describe a whole suite of desert-plant adaptations. Drought-resistant perennials include jujube, loquat, macadamia nut, mulberry, persimmon and pomegranate. True drought tolerance is a characteristic of deep-rooted, desert-hardy trees — such as carob trees and date palms — that can survive months without rain by extending their roots down and tapping into underground aquifers.
In the interest of precision, I propose one more category. Many herbaceous annual and perennial crops function as drought evaders in that they circumvent drought. They begin their life cycle with the onset of rains intense enough to trigger germination, and then complete the cycle before the brief wet season is over. They largely avoid desiccation and drought stress by ripening their fruit and dispersing their seeds well before severe soil and water deficits recur, so they never truly experience extended drought. Many early-maturing, short-season vegetables and grains employ these drought-dodging strategies.
Short-season crops have exceptional value in an era of water shortages and climate uncertainty because, after it’s transplanted in a field, a crop that matures in 60 days rather than 90 may require 20 to 25 percent less irrigation than its late-blooming counterpart, thus conserving water and energy.
The Drought-Tolerant Crops and Varieties chart indicates early-maturing, heat-tolerant varieties that avoid drought, pests, and early and late freezes, rather than attempting to withstand them. For example, short-season flour corns from the Sonoran Desert — such as ‘Tarahumara Harinoso de Ocho’ and ‘Onaveño’ — and even the ‘Gaspé Flint’ corn of moist, temperate Quebec will begin to tassel out and produce ears in 45 days, and will yield dry, fully mature kernels for grinding in about 60 to 70 days.
These examples from both the far Southwest and the far Northeast underscore that every region has some early-maturing crop varieties adapted to its prevailing growing season.
The most effective ways to enhance the resilience of food production in a climatically uncertain future are to:
1. Eliminate monocultures. Grow several varieties of the same (or related) species together in the same plots or fields. By mixing varieties that have different flowering times, frost or heat tolerance, and water requirements, you’ll be hedging your bets and preventing most stresses from damaging your entire harvest.
2. Plant drought evaders. Some of the elements of your crop mixtures should be early-maturing, short-season crop varieties that can germinate during brief wet seasons when soil moisture levels are temporarily adequate, thereby decreasing irrigation demands and lowering the risk of crop failure. (See the Drought-Tolerant Crops and Varieties chart above for a list of recommended drought-tolerant crops and varieties.)
3. Include perennials. Use intercroppings of annual and perennial species with diverse growth habits and from various plant families. This strategy establishes polycultures that collectively harvest more rain and sun, and use proportionately less groundwater and fossil fuel. For instance, by planting vegetables under canopies of fruit, nut or legume trees — a technique known as “alley cropping” — you’ll buffer the vegetable crops from temperature extremes and minimize potential danger from harsh climatic events such as hailstorms. Even so-called sun-loving vegetables, such as chiles, actually do better in some regions under the partial shade of mesquite, honey locust, cherry or plum trees.
Diverse crop mixtures share beneficial soil microbes as well. A motto for growing diverse agricultural crops resilient enough to fend off the threats of climatic disruption is: No annual grown alone, no perennial left behind!
4. Try intercropping. Many vining plant varieties, such as pole beans and watermelon, have already been selected for decades, or even centuries, to be suited to intercropping. Planted next to corn, millet or sorghum, they will climb right up the stalks. This helps produce the added harvests of edible produce that agro-ecologists call the “overyielding effect.” A good example of this is a Three Sisters garden of corn, beans and squash. The combined yield of this planting grown together on the same land is often higher than what any of these crops planted individually would produce in the same space.
5. Use your microclimates. Get to know your land and take advantage of any moderated microclimates. In other words, use your landscape’s terrain advantageously by matching crop needs with each agro-habitat.
6. Establish landraces. Create your own landrace crops — local varieties that have adapted specifically to the natural environment of your garden or homestead — by observing your garden carefully and saving seed from the plants that do best.
Gary Paul Nabhan is an agricultural ecologist, ethnobotanist and writer whose work has focused primarily on the desert Southwest. He is considered a pioneer in the local-food and heirloom seed-saving movements. This article was adapted from his recent book Growing Food in a Hotter, Drier Land: Lessons from Desert Farmers on Adapting to Climate Uncertainty.