|Photo by Peggy Wenrick, 7/31/11|
From this site:
"Because the saguaro is composed mainly of water, it is highly succeptible to damage caused by frost. Frost and freezing temperatures cause irreversible damage to the soft tissues of the saguaro. The damaged tissue rots and can weaken surrounding tissues, causing stems to shrivel or become wavy and arms to droop toward the ground. A prolonged freeze can permanently damage the growth cells at the tip. If the saguaro is able to recover, new arm buds can grow out of the damaged tip, but the connection between the two is not continuous and appears like a sausage link. Irreversible frost damage and death occurs when the saguaro is no longer able to protect healthy tissue from the bacteria decomposing the rotten, frost-damaged tissue. The decomposition spreads into the healthy tissue and destroys it, turning the rotten tissue into a black gelatinous mess that oozes out and runs down the exterior of the cactus. Saguaros can live from a few months to 9 years after the fatally damaging frost (Steenbergh and Lowe: 1983)."