Recent Hard Freeze Likely Will Be Death Knell for Many Weaker Saguaros

A prolonged freeze three weeks ago almost certainly was a death sentence for some members of a prized desert species: the saguaro cactus.

Biologists say similar freezes in the past killed saguaros, but it could take months or years before affected plants succumb.

They emphasize that damage or death would be most likely in very old, very young or diseased saguaros. By no means is a large-scale die-off expected.

"We're obviously very concerned about it, and we'll certainly be looking for signs of tissue necrosis--basically rotting of the cactus," said Don Swann, a biologist at Saguaro National Park. "It could take some time for that to show up--months or years, depending on the size of the cactus and the extent of the damage."

Temperatures dipped into the teens in the Tucson area during the first week of this month. That brought the kind of hard freeze that "certainly did kill saguaros in the park in the past," Swann said.

"There was a prolonged cold spell in 1971," Swann said. "Scientists working in the park at that time documented the effects and found that the freeze caused saguaro deaths. It tended to affect the oldest and the youngest ones."

Philip Jenkins, a curatorial specialist at the University of Arizona Herbarium, said he expects "some saguaro mortality" from the freeze.

The big questions now, Jenkins said, are: "How bad is it, and when are we going to see it?"


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Phillip Jenkins
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Released date: 
Mar 18 2011