Strolling through the El Paso Municipal Rose Garden on a March afternoon, horticulturist Eduardo Rascon pointed out healthy color changes in the leaves and scooped up a handful of pecan shell mulch, showing how the soil beneath it remains damp.

The first flush of blooms start to come in early April. Moisture retention is critical for the rose bushes’ overall health, and will be especially important for them to survive the upcoming heat.

Rascon said the roses struggled this past summer, when the city experienced a record-breaking 44 consecutive days above 100 degrees in June and July, as 2023 was the hottest year ever in El Paso

The majority of global warming in the last century has occurred since 1975, according to NASA. Humans continue to drive climate change by burning fossil fuels, which increase greenhouse gas concentrations.

As extreme weather events become more frequent, gardeners have to consider making adjustments in not only what they grow, but how they grow, Rascon said.

The U.S. Department of Agriculture developed a scale for mapping plant hardiness zones, geographic areas defined by average minimum temperature. Growers can use their zone to figure out which perennials – plants that come back every year – will most likely thrive in their area.

In November 2023 the USDA updated its plant hardiness zone map for the first time in more than a decade. Based on three decades of data, El Paso and about half the country shifted half a zone up because of warmer winters.

Most of El Paso changed from zone 8a to 8b, with areas such as Downtown seeing a 7 degree increase in average minimum temperature, while Northwest El Paso saw a 2 degree increase and a swath of the East Side saw a 5 degree increase.

Plants that grow well in El Paso

Rascon works as a county horticulturist for Texas A&M AgriLife Extension. The outreach agency works with El Paso County to provide educational programs and services. Topics the agency covers include mitigating drought impacts, conserving water and improving nutrition for public health.

There are other factors growers may face besides temperature fluctuations, such as tightening water restrictions. This creates a challenge for non-native plants, such as popular hybrid tea roses, that are susceptible to sun scorch and require frequent watering in hot climates, Rascon said.

Rascon recommends that gardeners place a layer of mulch, such as wood chips, around their rose bush, though not piled at the base. In the winter, mulching can protect the root zone from freezing, and in the summer mulching helps the soil retain moisture.

Desert-adapted plants aren’t as delicate in the heat because they have a different process for photosynthesis. These plants close their stomata, the pores on their leaves, to not lose water to evaporation during the day, and then open them up again at night.

At one end of the garden, Rascon pointed out the characteristics of desert rose, a type that grows in dry rocky places in the Southwest. When people picture roses they think of the bouquets they get in the store, Rascon said. But the desert has its own species of rose, which has smaller flowers, as well as smaller leaves and longer, denser thorns to reduce the surface area for water evaporation.

The El Paso Municipal Rose Garden has a mix of native, desert-adapted and non-native plants. Rascon encouraged people who have already established non-native plants to start growing climate resilient, native or desert-adapted plants too.

Hardy trees such as honey mesquite and palo verde have adapted and thrived in this region for thousands of years, surviving without fertilization and with limited rainfall, Rascon said. These trees also provide food for native wildlife and pollinators. They are fast growing, so they can start providing shade in 10 to 15 years, he added.

People can also set out shallow water dishes for pollinators, Rascon said. 

Other plants native to El Paso include the ocotillo, which in April bloom bright red flowers with a sweet nectar, and the four-wing saltbush, a hearty shrub with leaves that can be used as seasoning.

The Centennial Museum and Chihuahuan Desert Gardens published a list online of recommended Southwestern plants for the El Paso area.

How warmer winters affect plants

Home gardener Lanica Yu-Richardson said every home gardener should be conscious of climate change.

After Yu-Richardson left the U.S. Air Force and moved from Arizona to El Paso in 2010, she took up gardening to help transition into civilian life. The military gave her days structure. She yearned for more organization in her life and a way to relieve stress.

Yu-Richardson’s first attempts at gardening started in her yard, on an eroded hill with dry dirt, a few patches of grass, rocks, and barely alive roses. Eventually she developed a green thumb thanks to a combination of gardening mentors, books, online research and local resources including Desert Blooms El Paso, a water-efficient landscape guide for the Chihuahuan Desert.

In 2018 she started Color the Desert w/ Lani: El Paso Gardening, a Facebook group with more than 6,300 members where people can share and ask for gardening advice.

“American society teaches us to be reactive, not proactive,” Yu-Richardson said. “We gotta do our part before we have a mass extinction. We need to be good stewards of the natural resources that we have. We’re a very instant gratification species. We will use every single resource and destroy natural resources to get what we want.”

People tend to think of warmer winters as a longer growing season, Yu-Richardson said. But rising minimum temperatures can alter the chain of life.

Stone fruit trees – such as apricots and nectarines – require a certain amount of chill hours to stay dormant, she gave as an example. After a sufficient amount of chill dormancy, the trees can start budding and developing leaves.

Without enough chill hours, the trees may not “wake up” at a certain time frame and bloom, she explained. This can create a mismatch in timing with pollinators, such as bees and hummingbirds, that won’t have anything to eat. If pollinators die off, the plants that depend on pollination die off, then the animals that eat those plants die off, and so forth altering the food system.

When it comes to gardening groups, people tend to focus on their specific plant or yard, Yu-Richardson said. But she hopes that by sharing more big-picture information in the mix, people will want to learn more about how climate change affects future generations and the world beyond their own personal garden. 

“People are like, ‘Oh, it’s hot. So what’s one more degree?’” Yu-Richardson said. “It’s just short-term thinking.”

Rajan Ghimire, a soil scientist at New Mexico State University, used a full bathtub as an example of how average temperature increases affect plants.

A person can fill a bathtub drop by drop, but once the bathtub is full, there is a point when the water will spill over, Ghimire said. For many crops, photosynthesis plateaus at 30 degrees Celsius, or 86 degrees Fahrenheit – so going from 30 to 30.1 degrees makes a bigger impact than going from 20 to 29 degrees, he said.

“It’s small, but it still matters,” Ghimire said.

During photosynthesis, plants use sunlight, water and carbon dioxide to create chemical energy and oxygen – the source of survival for all living organisms.

Climate change impacts food security

Ghimire is an associate professor and research director at the NMSU Carbon Management Center, where he focuses on conservation measures to minimize the impact of climate change. He works with farmers to help them better manage their soil health and adapt to increasing drought conditions.

Along with the change in USDA plant hardiness zones, which are based on temperature, New Mexico and Texas are also seeing more variability in extreme weather events. Temperature changes also affect precipitation and seasonality, but there’s still a lot of uncertainty about the extent, Ghimire said.

Some crops in southern New Mexico are already at the tipping point. As temperatures continue to rise, farmers in the future may have to transition to new crops that are better adapted and give up more sensitive vegetables, Ghimire said.

Improvinging soil health can help plants absorb nutrients and water better. A preliminary 2022 study suggests that healthier soil also leads to more nutrient-dense food.

Ghimire said certain practices are beneficial for soil.

• Crop rotation: Planting a different crop on the same piece of land each season.
• Cover cropping: Growing plants to cover the soil rather than for harvest. These plants can replenish lost nutrients and help improve soil health for the success of future crops.
• Tilling management: Heavy and poorly planned tillage disrupts the structure and organic matter in soil, accelerating soil erosion and surface water runoff.

“Farmers are dealing with a lot of (environmental) stress and very thin margins,” Ghimire said. “If there’s any more stress, they cannot make their farming profitable. We need to work on the policy front.”

More policies and subsidy programs that support farms doing climate-smart practices would provide an incentive to other farms to adapt those practices, he said.

Yu-Richardson said the city of El Paso and local groups could get more involved to promote sustainable practices too. She pointed to a program in Phoenix, where public utility company Salt River Project teams up with Trees Matter, a nonprofit, to provide home owners and renters with two free “desert-adapted, drought-resistant” shade trees. Participants attend a workshop to learn how to care for their tree.

Free seeds from El Paso Public Library and free mulch from the city’s  Citizen Collection Stations helped get her garden in shape, Yu-Richardson said.

Gardeners should consider the plants that will ultimately thrive in the long run, Rascon said. He recalled the inquiries he received last year, when El Paso was experiencing periods of high heat.

“People were calling because their non-native trees were having issues with that fluctuation,” Rascon said. “Nobody was calling for their honey mesquites or their palo verdes or those other native trees. They can take those extreme temperatures and bounce back or not really be affected by them.”