cactus turning brown - suspect overwatering

 

Hi, I have a very old cactus that I don't water often.

I noticed this week the new growth at the top is going brown (an
unhealthy brown) on one side. The cactus is about 3.5 foot tall - the
last 5" are affected.

I suspect it's overwatering as it turns out someone has been watering it
for me (a kind gesture but...).

Obviously I'll stop watering it for a while... a long while!

Does anyone know if they generally recover? I've never been in this
situation before.

Thanks a lot,

Craven.

 


I have (very nearly "had"...) a Cleistocactus straussii which I'd had for 20
years, and was always treated the same way.  It had 3 stems - each 4 - 5 cm
in diameter and about 120, 90, and 30 cm high, and flowered every year.
Last year the tallest stem started to go soft at the top, and gradually died
back.  Despite cutting it back well below the damaged area, it still kept
going soft (even though it was kept completely dry, and it was by now
summer) and continued to die back.  The next tallest also now started to go
soft, and eventually the shortest stem did too.  I cut them all back to
about 10 cm.  I couldn't tell if they had stopped dying back, but as I hate
to chuck anything away, I stuck it under the bench.  A couple of months ago
I looked at it. There was no further change to the 3 stems as far as I could
see, but a new stem had appeared from below soil level!  That is now about 3
cm high, and looks healthy.

I have no idea what happened to my cactus, but it may be worth you doing the
same thing to yours if you think it will save it.  What species is it?

By the way, is the brown area hard or soft?  If it's soft, it may well be
rot or another fungal disease.  If it's hard, and a bit scabby, I have heard
it said that it can be due to a trace element deficiency.  In the latter
case, the cactus should grow through the problem and start turning green
again. Whatever, if you don't water it again until next March or April it
can't do any harm.

--

Jeff

 



As Jeff says, they often come back to life when least expected.  You could
try ripping a live bit off the side, if you have a spare bit, let it dry out
for a while, and then stick it in vermiculite to see if it takes root.  So
then you'll have two!

I have a lot of epiphyllums and they go scabby from time to time, I didn't
know that it was a trace element deficiency, thank you for that, I shall
have to feed them more.

someone

 

On 04/08/2010 21:16, Craven wrote:

A picture would be useful. Rotting from the top is unusual. Noticing
when the rot which started from the roots reached the top is more common.

If it is overwatering then the soft rot starts at the roots and works
upwards. A tall plant tends to fall over if this happens. In summer it
is hard to overwater unless you leave them standing in water for ages.

It is hard to kill a cactus by underwatering. I had one ~4" diameter off
its roots for a year and thought it was dead and shrivelled up. It was
sat unpotted for a season and then came into flower as its last defiant
act. Potted it up again at that stage and it rerooted.

I don't recommend this method of cultivation.

Hard to tell. If it is just going brown then it could be scarring from
pest damage at the growing point rather than a rot. A picture would help!

Regards,
Martin Brown