My cactus has been grown from seed and has lived about five years. Over the past several months it has turned yellow- I read that it may be a case of root rot/overwatering so I’ve not watered it in several weeks and it is continuing to die. The plants “sister” (same species, planted at the same time) is fine and has the same watering schedule. Should I water it, leave it, or accept that it’s going to die? I’m quite attached to him and would rather he live.
I'm going to guess that the container this plant is in does NOT have a drainage hole. It needs to be in freely draining soil with a hole or holes in the bottom for excess water to escape. Without seeing the bottom of the stem it's hard to tell if it's rotted or just yellow.
My guess is that it is either rotted or needs better living conditions including fertilizer.
From the picture it doesn't seem to be shrunken and the yellow color is definitely better than black or brown.
Has anything changed about it's condition/environment? Repotted? Moved to a sunnier window, anything?
The top half inch looks great, though!