Need some advice - Discoloration, disinfection

[The Matt Hatter]

Hello guys,

New to the group, and I'm looking for a bit of advice. I actually have two things I need help with, and hoping that's ok.

The first thing I need help with is discoloration.
I have a 43 y.o. golden barrel cactus that recently acquired, and it seems to be yellowing from the bottom up.

It was an indoor cactus until I got it, and I've been keeping it in the yard, under the canopy for a few weeks. I've since noticed it's starting to yellow. It hasn't gone soft or soggy.

I'm thinking it may be heat stress or humidity stress, but maybe some of the more experienced keepers could help me with this issue.

I've uploaded photos of the cactus. Some with natural light, and some with flash to better see the discoloring.


The second question I have - I have some mildew showing up on a few of my cacti, and I'm wondering, is it safe to use hydrogen peroxide or rubbing alcohol to disinfect?

I've done with before successfully with other house plants, but not sure how the cacti/succulents will react to the alcohol/peroxide.

Any help is greatly appreciated, and if there's any details I forgot, or additional info, just let me know.

Thanks everyone!

[MikeInOz]

I suspect that the roots are not active enough to sustain the plant well. The bottom part looks quite hard and corky and you can bet that the roots are not in a vigorous condition. If this was mine would cut it off to nice healthy tissue and re-root it. Of course this has to be done at the right time of year and you need the necessary patience to properly season the wound and allow it to root down in it's own time. The whole process may take 6 months.
I frequently do this with old plants which have slowed down due to inactive old roots.

[anttisepp]

Stem colour change is due to change of conditions IMHO. I'd continue the same way cause much more light is healthier for plant and it will correct its shape at last - "neck" will be shorter and "head" more depressed, not elongated.
H2O2 3% is nice for plants.

[The Matt Hatter]

I suspect that the roots are not active enough to sustain the plant well. The bottom part looks quite hard and corky and you can bet that the roots are not in a vigorous condition. If this was mine would cut it off to nice healthy tissue and re-root it. Of course this has to be done at the right time of year and you need the necessary patience to properly season the wound and allow it to root down in it's own time. The whole process may take 6 months.
I frequently do this with old plants which have slowed down due to inactive old roots.

Do you think there's anything I could do to improve root structure without cutting it?

I just don't know how comfortable I would be operating on it like that. I've taken cuttings for clones before, but never anything to that extent.

[The Matt Hatter]

Stem colour change is due to change of conditions IMHO. I'd continue the same way cause much more light is healthier for plant and it will correct its shape at last - "neck" will be shorter and "head" more depressed, not elongated.
H2O2 3% is nice for plants.

Ya, I figured that having it outside would be good for it, as my others have done great outside. I figured with it being so old, it would be fairly hardy, but I may have misjudged.

The older cactus at the base had already died off when I got it, but the yellowing has progressed kind of quickly. With the humidity and intense sun we've had lately, I didn't want to risk it, so I brought inside. It's under a T5 full spectrum with west window lighting. I'm hoping this will let it dry out/cool off.

Or do you think it might be fine outside despite the discoloring?

[MikeInOz]

Do you think there's anything I could do to improve root structure without cutting it?

I don't think so. If you are worried about cutting, then just leave it and see what happens.

[ohugal]

I have an echinocactus grusonii of which the discoloration and corking resembles yours. It was first not getting enough light and shortly after moving it onto an outside window sill it got sunburned. I've also had high humidity levels and poor air movement at a certain point. I try to balance it out with ventilation (open window) or a dehumidifier (which also provides air circulation). After checking the roots and repotting, it continued to grow healthly. It is unsightly though and a living reminder bad parenthood. How are the roots looking?

[The Matt Hatter]

I have an echinocactus grusonii of which the discoloration and corking resembles yours. It was first not getting enough light and shortly after moving it onto an outside window sill it got sunburned. I've also had high humidity levels and poor air movement at a certain point. I try to balance it out with ventilation (open window) or a dehumidifier (which also provides air circulation). After checking the roots and repotting, it continued to grow healthly. It is unsightly though and a living reminder bad parenthood. How are the roots looking?

I haven't had the heart to dig up or repot yet tbh.

[The Matt Hatter]

Update:

After bringing it back inside and under the light, it seems to be bouncing back. the yellowing seems to be fading, and it's taking more of its original deep green.

I'm not sure if it's the humidity, or Sun, but I think I'll ever on the side of caution and maybe slowly acclimate this guy to the outdoors for the rest of this season, and give him a go again next season.

Thanks again for the input and advice guys