Expert: Maureen - 12/29/2010

Question
QUESTION: I am not sure of the type cactus I have, but it is about 6-7 feet tall and has about 3 "arms".  I have had this cactus for about 5 years.  Recently I noticed the base of the cactus is turning brown but unlike other questions I have read, the base does not seem soft.  The texture is normal, only the color is changing.  The brown has now traveled about two thirds way up the cactus.  I have not changed any watering habits so I don't think it is over/under watering.  What is wrong with this cactus and is there any way to save it?

ANSWER: Dear Nathan,

It is hard to tell with out seeing the plant but what it may be experiencing a process called corking.
It is just a natural aging process of cacti. As the cactus matures, the lower parts or base of the plant turns from smooth-green skin to a tough, brown, bark-like appearance. Corking starts from the base of the cactus and works up the plant. If a cactus is turning brown from the top down, or in spots on the side or in the middle, then it is not corking, but a real problem such as spider mite or sun burn.

Why don't you google it and see if that's what's going on with your plant.  If not, send me a photo so I can get a look at it.  It does sound like corking, tho.  I hope you are repotting that monster every couple of years!

Maureen

Treatment

---------- FOLLOW-UP ----------

QUESTION: I have attached a picture.  Some of the brown area has turned hard and almost sounds hollow if you tap it.  Can you also tell me what kind of cactus this is?  I hope there is a chance of saving it or at least part of it.

Answer
I still think it's corking, Nathan.  The other possibility is dry rot.  I'd leave it alone for now and in the spring unpot it and look at the roots.   If they are dead and the main stalk is completely dry and brown than it's rot.  What you can do is cut off the healthy arms, let them callous and root them.  if you look through what I've written there's lots of info on that.

I am not sure if you have a Euphorbia or a cactus.  Would need a close up of the spines.

Maureen