Question
I saw a similar question on this site about a candalabra cactus but with mine the lower central stem is rotting and it has moved up one branch.  There is another green healthy stem about 4 foot tall which starts a bit further up but is connected to the central branch.  I have had this cactus about about 23 years and would like to try and save it.  Can I cut off this 4 foot branch and root it?  This is an indoor cactus - if I can root it what size pot should I use and what kind of fungicide do I use on the cut portion.

Thanks for your help.

Jeanne

Answer
Dear Jeanne,

Do you have a photo?  How do you know it's rotting?  What does it look/feel like? The reason is that sometimes older cacti will develop corking and folks mistake that for rot.  I am wondering why it is rotting agter 23 years.

To answer your question, yes, you can root the arm as long as it doesn't have rot.  Take a sterilized knife and cut it off where it meets the main stem.  Dust with fungicide and let it callous over - at least a couple of weeks.

Plant it in a soilless mix slightly moistened in a pot that is large enough to let it stand up straight.  You may have to initially support it with stakes.  Plant a few inches deep. Then don't water again till you see new growth.  You can mist it occasionally if you like.  It take take a long time to root, but you will see new growth when it has.  Takes months sometimes.  Then start to slowly water. The rule of thumb with a columnar cactus is that the pot is 1/3 the height of the plant so the pot is always a bit wider and deeper than one normally wants for cacti.

You can also cut above the rot on the main stem and root that.  I'd let it dry out longer before you plant it assuming it's a wider piece.  Just make sure the tissue is clean, no brown, yellow, mush etc.  If you have to make more than one cut, sterilize the knife with each new cut.

If I can help you further, please don't hesitate to let me know your questions.

Maureen