My roommate was trying to "help me" care for my indoor garden, and without me knowing about it, was watering my moon cactus. I noticed my cactus was looking sad a few days ago. Its stalk is an off color (not completely brown, but its dark green, definitely not healthy) and is slightly soft. Then I noticed the soil was moist. Its winter and very cold here, probably close to 50-60 in the apartment at night (I've been keeping it by a UVB light at night too). I've had her stop watering it since, but is there anything I can do to save it?
It sounds like it may be suffering from the onset of root rot--a result of too much water. Perhaps you should explain to your friend that succulent plants should only be watered when their soil has dried out. At any rate, this article will help with root rot: https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm
The top of my moon cactus began to shrivel and leak, so I removed it from the rootstock. Instead of grafting something onto it, is there anything else I can do with the stock? Also, what type of soil is best for these types of cacti?
The moon cactus needs to be grafted onto another rootstock because it lacks the ability to photosynthesize - meaning it can't make its own food. Here are a couple of articles that will help you if you want to try regrafting yours: https://www.gardeningknowhow.com/ornamental/cacti-succulents/moon-cactus/care-of-moon-cactus.htm
I have a grafted cactus that I picked up at Lowes on the discount shelf. The bottom portion or the rootstock had a gash in it. It has since turned brown and squishy. It can't support the top part which appears healthy. What can I do at this point to bring it back or at least save the top?
When a cactus - or any plant, for that matter - is brown and squishy, it's dead, and there's no saving it. You might, however, be able to regraft the yellow top onto a new cactus. It has to be grafted because it has no chlorophyll so it can't make it's own food. This article will help you with that project: https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/grafting-cactus-plants.htm
I have an indoor moon cactus which is healthy except that over time the red color has faded. How can I get it to be bright again?
Little can be done to return it to it's original color.
Sunlight fades the top as it does not produce chlorophyll.
My girlfriend just bought me a moon cactus and I have no idea how to take care of it. How often should I water it and what is this grafting thing I'm hearing about? Thanks.
Here is a link that will give you all the care requirements.
Got one and it turned brown from red. what did I do wrong?
A Moon Cactus is actually grafted onto the base of another cactus. This can make for a weakened cactus, making is susceptible to root rot.
If the stem has turned brown, it is generally root rot and likely cannot be saved.
Bacterial or fungal infections can also attack the cactus and cause it to turn brown.
In general if the plant has turned brown and is soft and mushy, it is best to discard it and start over.
Here is a link to refresh you on the care requirements.
I was given a Red Top moon cactus recently and the roots are now coming out the bottom of its pot, which is the original pot. Can it be transplanted and, if so, what size pot?
Yes, the plant can and should be repotted. You can move it into a pot that is 1/3 to 1/2 size larger than the pot the plant is currently in. This article should help you: