Question
I have what I believe is a Euphorbia trigona, which I purchased about 25 years ago.  (It was about 6 inches tall when I purchased it; it is now 52 inches tall).  Unfortunately, it was significantly over-watered a few weeks ago.  Shortly thereafter, the first several inches at the base became extremely wet and soft and the cactus folded and fell over.  I propped it upright and tied it to a rod.  Now, the lower portion (the bottom 22 inches) of the cactus is dry, shriveled and crackly -- and the dryness is working it's way up the cactus.  I would like to replant and save it -- but do not know how.  The lower 22 inches appear to be dead.  But, the top 30 inches are still green.  Can I sever the lower portion from the upper and replant?  There appears to be a natural indentation or dividing point where I could cut it.  If I cut it there, how do I replant?  

Answer
Glenn,

Yes you can transplant the top portions. However, depending on how long it has been like this, it may not root before the tops completely dry up.

Euphorbia's have a poisonous sap called latex inside, so a better idea is to break off the top sections just below the green parts. That will minimize the sap release and decrease the "scab over" time.

Break off all you want to and set them aside for a couple of days. Get a pot that will hold them or a few pots to hold them. Use a "cactus mix" type of soil and plant them so about 3 inches of the green part is under the soil. Water, then don't water again until the soil is dry.

If they root, it will take a month or more. You will probably lose quite a few, but a few should root. Keep them out of direct sunlight and above 50 degrees. Hopefully this helps and good luck!

Sincerely,

Greg