After recording the warmest monthly average temperature for any American city ever in July, Phoenix climbed back up to dangerously high temperatures on Wednesday. That could mean trouble not just for people but for some of the region’s plants, too.
Residents across the sprawling metro are finding the extended extreme heat has led to fried flora. 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. “A lot of people are calling and saying their cactus is yellowing really hard, fell over or like broken arms, that sort of thing. Twenty-year-old trees are losing all their leaves, or they’re turning a crisp brown.”
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 102.7F (39.3C) – turned out to be the cactus needle that broke the camel’s back.
Saguaros can live up to 200 years and grow as tall as 40ft (12 meters). Some in the Desert Botanical Garden date beyond its opening 85 years ago, and the largest there measure almost 30ft (9 meters), according to Kimberlie McCue, the garden’s chief science officer.
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 110F (43.3C), but also the multiple nights when the low never dipped below 90F (32.2C). Night-time is when cactuses open their pores to get rid of retained water and take in carbon dioxide, she explained.
There is hope that the arrival of thunderstorms during the monsoon season, which traditionally starts on 15 June, could bring more delayed moisture that will help struggling flora.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.
As of Wednesday, there was no rain in the forecast for Phoenix anytime soon according to the National Weather Service. After two days of a slight drop, high temperatures reached 111F (43.9C) and are expected to be 110F or more for the next 10 days.
The Weather Service plans to issue an extreme heat warning Friday through Monday, when the highs will be between 111F (43.9C) and 117F (47.2C).
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In the meantime, the Desert Botanical Garden has been working to propagate cactuses that seem better able to endure searing conditions after staffers noticed the 2020 heat was more difficult for some plants than others. Some just seemed to have a genetic makeup that allowed them to thrive.
“We want to try and capture that and grow more saguaros from seed here to add into our population at the garden with the idea that over time, that is going to bring more resiliency into our population here,” McCue said.