my 40 year old cactus are turning mostly white with some brown markings. Can these cactus be saved? if so, how?

Question

These are outdoor 8 foot cactus in pots.  The night temps drop to 30's so I have drapped them with a cloth designed for outdoor plants in the winter.   They get watered once or twice a month and do not look like insects have caused my concerns.

Because they have been in these pots for 6 years, could it be the soil has zero nutrients let ?    Can these cactus be saved?  If I cut them back to where there is still green plant , would that be helpful?

Thanks for your advise.

Answer 1

Okay so listen to this answer and try it, if you do nothing the cactus is doomed.  However, I personally had the same problem when my mother passed and I got the plant that no one wanted.  Every morning I empied the remaining coffee into the plant, I did this for about 3 1/2 months, the spent coffee (not the grounds) addecd just the right amount of neutrients back into the soil that the Cactus thrived and actually grew more than 1 1/5 foot taller and added just under 3" at its base.  Now, that same cactus ghraces my office near my desk and is still alive, it has been watered 2x a month now for 9 years with coffee, it is doing quite well.  Something to think about.