On 10/04/2013 14:49, CactusPaul wrote:

I have had this cactus since i was 9. It is now 22 years old and in big
trouble. I have come back from travelling for 3 months and it is in a
terrible condition. It has been in the greenhouse over the winter months
and i fear this has contributed to the damage. It appears to be rotten
at the top as half of steam looks eaten away. The bottom i am not so
sure of. I gather that some breads do tend to go a little brown at the
around the bottom anyway. I am just wondering what the best course of
action is. Can i cut the top off where it is rotten? If so, should i do
this and repot the remainder of the plant? Any advice would be most
welcome as i have previously had no trouble with the plant so i am not
knowledgeable about treating them.

Before you do anything a picture would be useful. The best thing to do
might be nothing as some cacti can recover on their own from cold
damage. They will always look scarred afterwards but stay alive.

However, fungal rot from overwatering or cold damage to a sensitive type
that needs semitropical arid conditions is often fatal. A picture and
knowing its shape would be very very useful so that we can ID it and
then offer appropriate advice. If it is fungal rot you have to get every
last trace of rot which tend to show as brown or orange.

Rotten from the bottom is usually more common. A big globular cactus can
survive and astonishing amount of time with no roots. I had one I
thought was brown and dead after chopping it off rotting roots that I
only realised was still alive when it threw out a flower spike six
months later. Last act of desperation - putting it on well drained
compost and grit it rerooted and grew on with a growth check ring.

Three of the cacti I had as a youngster are still alive. One an opuntia
lives in an unheated greenhouse that is falling down around it at my
parents. The thing flowers every year despite the adverse conditions.

The other two are columnar cereus that are as tough as old boots and
survived 3 years in storage as "house plants" when I lived and worked in
Japan followed by house moves to and from Belgium. One of them about 2m
tall put a spine right through the nose of one of the house movers as he
went to lift it. His mates thought it was hilarious. I expected him to
have given the thing a good kicking out of sight in the back of the van
but it survived the journey back unscathed.

Even if it looks dead hang onto it for a while and you might be lucky.

If it is the sort of plant with pups on grab a couple off it now and try
to root them as an insurance policy.

--
Regards,
Martin Brown