Question
I have had my cactus for 3 years now. It is about 5ft 7in and it is my pride and joy.  I have noticed that at the bottom there is some white discolouration and the stem is quite soft. some of the extra bits coming out of it are starting to sag.  please can you tell me what's wrong with it and most importantly what I can do to help it.
Thank you so much.

Answer
Dear Amy,

I don't have good news for you. Based on your description, it sounds like it has started to rot. However, rot is usually black, not white. Sometimes sunburn can start out as white though. Can you tell me the name of your cactus? That would help me immensely. If your plant is a Euphorbia rather than a cactus, that would makes sense (my rot theory). Please let me know as soon as you can, as time is of the essence.

Sincerely,

Greg