Coping With Heat in the Garden: Drought-Tolerant Crops, Resilient Perennials and More
Coping With Heat in the Garden: Drought-Tolerant Crops,
Resilient Perennials and More
You can employ several strategies for growing food while
coping with drought and climate change, including planting dozens of
recommended varieties of short-season, more drought-tolerant crops.
June/July 2014
http://www.motherearthnews.com/homesteading-and-livestock/drought-tolerant-crops-zm0z14jjzcom.aspx
By Gary Paul Nabhan
Fruit and nut trees buffer vegetable crops from temperature
extremes.
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.
Crop Resilience
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 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.
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