PHOENIX (AP) — After recording the warmest monthly average temperature for any U.S. city ever in July, Phoenix climbed back up to dangerously high temperatures Wednesday. That could mean trouble not just for people but for some plants, too.
Residents across the sprawling metro are finding the extended extreme heat has led to fried flora, and have shared photos and video of their damaged cactuses with the Desert Botanical Garden. Nurseries and landscapers are inundated with requests for help with saguaros or fruit trees that are losing leaves.
Phones have been “ringing nonstop” about everything from a cactus to a citrus tree or ficus, said Sophia Booth, a landscape designer at Moon Valley Nursery, which has nearly a dozen locations across the Phoenix suburbs.
“A lot of people are calling and saying their cactus is yellowing really hard, fell over or like broken arms, that sort of thing,” Booth said. “Twenty-year-old trees are losing all their leaves, or they’re turning a crisp brown.”
She advises people to give water and specialty fertilizer to a distressed tree or plant every other day and not to trim them.
At the Desert Botanical Garden, three of the treasured institution’s more than 1,000 saguaro cactuses have toppled over or lost an arm in the last week, a rate that officials there say is highly unusual.
These saguaros, a towering trademark of the Sonoran Desert landscape, were already stressed from record-breaking heat three years ago, and this summer’s historic heat — the average temperature in Phoenix last month was 102.7 degrees Fahrenheit — turned out to be the cactus needle that broke the camel’s back.
“Since 2020, we have had elevated mortality in our population of saguaros compared to mortality rates pre-2020,” said Kimberlie McCue, the garden’s chief science officer. “So part of our thinking is that there are still saguaros today that were compromised from what they went through in 2020. And that this could be sending them over the edge.”
Saguaros can live up to 200 years and grow as tall as 40 feet. Some in the Desert Botanical Garden date beyond its opening 85 years ago, and the largest there measure almost 30 feet, according to McCue.
People commonly assume that cactuses are made to endure scorching heat, but even they can have their limits, McCue said. It wasn’t just this summer’s 31-day streak of highs at or above 110 degrees Fahrenheit, but also the multiple nights when the low never dipped below 90 degrees. Nighttime is when cactuses open their pores to get rid of retained water and take in carbon dioxide, she explained.
“With water loss, if they become dehydrated, that can compromise the structural integrity that they have in their tissues,” McCue said.
A cactus’ size can also influence its susceptibility, said Kevin Hultine, the garden’s director of research, and bigger plants with more mass are more prone to the effects of heat and drought.
“Larger (and older) plants have more arms and thus, they tend to be the first to start to lose structural integrity,” Hultine said via email. “The first sign of heat-related stress in a population are arms falling from large plants. Eventually, the entire plant might fall over from the stress.”
There is hope that the arrival of thunderstorms during the monsoon season, which traditionally starts June 15, could bring more delayed moisture that will help struggling flora. The U.S. monsoon is characterized by a shift in wind patterns that pull moisture in from the tropical coast of Mexico. It sets up differently in other parts of the world. In Arizona, about half the rain that falls during the year comes during the monsoon.
It can be a mixed bag — cooling sweltering cities like Las Vegas and Phoenix but bringing the risk of flooding to mountain towns and low-lying deserts alike. It carries a promise of rain but doesn’t always deliver. And even when it does, the moisture isn’t shared equally across the Four Corners region and beyond. The last two seasons were impressive, and the two before that largely duds.
