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Don’t Hug the Teddy Bear!


Teddy-bear cholla (Cylindropuntia bigelovii)

Just the thought of summertime in the desert conjures images of shimmering mirages induced by searing heat, endlessly shifting sands, rattlesnakes coiled and poised to strike and, lest we forget, the porcupines of the plant kingdom – spine-laden cactus.

A desert summer, away from the 24/7 AC, endless trays of ice and the deep end, can be a hostile season in a seemingly barren land with a paucity of life-nurturing resources. T e most precious resource, the one thing no living being can do without, is water. T e omnipresent task of all desert denizens is the procurement and miserly use of that life-sustaining liquid. T e keys to survival in a desert land are the adaptations to the scarcity of water: how to get it, how to get by on less and how to keep it once you have it. Cacti, one of the words nearly synonymous with desert, have become very effi cient at coping with and even thriving in arid climates.

Cacti are known universally for their water storage capabilities and some species can be 97% water by weight.

T is makes them a part of a large group of plants, known as succulents, which have specialized tissues in their roots, stems or leaves capable of sequestering water for future use. All cacti are succulents (except for the more primitive cacti, the Pereskia) but not all succulents are cacti. As astounding as their capacity for holding water, or maybe more so, is their ability to lose it. Some species of cacti can lose 70-80% of their weight due to dehydration before suff ering irreparable damage. By comparison, a loss of 30% can prove fatal to tissues in other plants and 15% can be lethal in humans.

Cacti are extremely adept at taking advantage of even light desert showers with their shallow wide spreading root systems. Most of the root mass is within four to six inches of the surface, seldom deeper than ten. Roots avoid the upper one and half inches of soil which is used as a buff er against potential ground surface temperatures of 160 degrees F or more in the summer. Noticeable growth of rain roots can take place within hours of soil rewetting. T ese ephemeral roots quickly increase the root mass for water uptake and are shed at the fi rst onset of drought. 11

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