Even cactuses feel burn of harsh Arizona summer

Certain cactus species can whither under the Phoenix sun, said arborist Scott McMahon, who has taken care of cacti at Desert Botanical Gardens since 2001. Cactus often pause in respiring – “breathing” water vapors and carbon dioxide – to conserve water in response to extreme heat, McMahon said. If the heat level doesn’t reach low enough temperatures at night, “they’ll essentially cook, just stewing in their own juices.” (Photo by Chris Benincaso/Cronkite News)

Certain cactus species can whither under the Phoenix sun, said arborist Scott McMahon, who has taken care of cacti at Desert Botanical Gardens since 2001. Cactus often pause in respiring – “breathing” water vapors and carbon dioxide – to conserve water in response to extreme heat, McMahon said. If the heat level doesn’t reach low enough temperatures at night, “they’ll essentially cook, just stewing in their own juices.” (Photo by Chris Benincaso/Cronkite News)

Even a cactus has limits.

The Arizona icon of desert survival can’t always take the heat. Record-breaking temperatures that draw shudders and international attention also have been rough on many types of succulents.

“Certain deserts are so harsh that even cacti won’t live in them,” arborist Scott McMahon said, who has overseen the cacti at Desert Botanical Gardens in Phoenix since 2001.

Workers cover vulnerable species with black nets to protect them from the sun, especially if they’re not native to the Sonoran Desert. But even native Arizona species have encountered more trouble with each passing summer, he said.

“If the heat is too severe they will stop growing,” he said. Cacti require temperatures of about 85 degrees at night so they’re able to respire, the plant equivalent of breathing.

If nighttime temperatures remain too high the plants’ water reserves will slowly be depleted.

“They’ll essentially cook,” McMahon said. “They’ll just sort of stew in their own juices, and after several weeks of this they will die.”

Direct sunlight also threatens succulents’ health.

“When this gets too intense it’ll burn the tissue and actually kill it,” McMahon said.

One cacti remains scrappy under the Arizona sun.

Saguaros, cactus royalty, store water so efficiently they can endure what other cacti can’t handle.

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