Question
I bought a cactus in Arizona called a fairy castle cactus. It's really neat, and I carried it on on the airplane. It was wrapped by someone who knew what he was doing. After a few weeks at home, It turned totally brown. I knew it was still alive, b/c most of it was still plump, save a few pieces. Now, alot of green has reappeared, but I think it's mainly new growth. However, it's mainly still brown. Can you tell me what happened to it? I'm apprehensive to do something about besides just watering once a month, because I'm afraid it will die and I won't be able to replace it.

Answer
David,

The fairy castle cactus (Cereus tetragonus) is fairly common. But yours sounds like it may have either been sunburned or heat burned. Sunburn usually results in white marks. Heat burn (which usually occurs when a cactus is left in a car) usually leaves brown marks. Typically, your plant is greenhouse grown, which means no direct sunlight or temperatures above 100 degrees. Once it heals, it should be fine, just not very pretty. Hope this helps.

Sincerely,

Greg