Chris Benincaso

Tuesday, July 11, 2017

Cacti feel the burn of harsh Phoenix summer

PHOENIX – 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 Phoenix 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.

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. (Photo by Chris Benincaso/Cronkite News)

Cactuses are covered with black nets to protect them from tissue damage because of the blazing summer sun, McMahon said. (Photo by Chris Benincaso/Cronkite News)

Tracey Rhodes, a horticulturist at Phoenix Desert Botanical Gardens, spreads a net over a yellowing whale’s tongue cactus. (Photo by Chris Benincaso/Cronkite News)

Even native species like prickly pear cactus rot and die under record breaking summer temperatures, McMahon said. (Photo by Chris Benincaso/Cronkite News)

Shin dagger agave is native to Phoenix but it too is yellowing. If the bleaching continues and gets more intense the plant may die, McMahon said. (Photo by Chris Benincaso/Cronkite News)

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)

The saguaro stores water so efficiently it can withstand scorching temperatures that whither other cactus species, McMahon said. (Photo by Chris Benincaso/Cronkite News)

Cacti growing in the limited shelter of larger plants often thrive and bloom. (Photo by Chris Benincaso/Cronkite News)

The lusher coloring of this whale’s tongue agave also shows the perks of shady neighbors for cacti. (Chris Benincaso/Cronkite News)

A bird mines the fruit of a cactus in bloom at Desert Botanical Gardens. McMahon said cacti and birds depend on one another. Birds eat cactus fruit and spread the seeds. (Photo by Chris Benincaso/Cronkite News)

(function ( $ ) {
“use strict”;

$(function () {
var masterslider_a99b = new MasterSlider();

// slider controls
masterslider_a99b.control(‘arrows’ ,{ autohide:false, overVideo:true });
masterslider_a99b.control(‘slideinfo’ ,{ autohide:false, overVideo:true, dir:’h’, align:’bottom’,inset:false , margin:10 });
// slider setup
masterslider_a99b.setup(“MS59655fd43a99b”, {
width : 800,
height : 500,
minHeight : 0,
space : 0,
start : 1,
grabCursor : true,
swipe : true,
mouse : true,
layout : “boxed”,
wheel : false,
autoplay : true,
loop : true,
shuffle : false,
preload : 0,
heightLimit : true,
autoHeight : false,
smoothHeight : true,
endPause : false,
overPause : true,
fillMode : “fill”,
centerControls : true,
startOnAppear : false,
layersMode : “center”,
hideLayers : false,
fullscreenMargin: 0,
speed : 20,
dir : “h”,
parallaxMode : ‘swipe’,
view : “basic”

window.masterslider_instances = window.masterslider_instances || [];
window.masterslider_instances.push( masterslider_a99b );