My barrel cactus has started tilting over the past few months even though it's in a stable pot. I water it maybe once a month and it gets plenty of light. Is it getting root rot, or do I need to stake it somehow?
Don't stake it or repot it right away - leaning almost always means the plant is phototropic and stretching toward light, not rotting. I had a barrel cactus do exactly this on a shelf that only got morning sun from one direction, and once I rotated it regularly and moved it closer to a south-facing window, it straightened up over a couple of months as the new growth came in more balanced.
I've dealt with this before - usually the lean happens because the cactus is growing toward its light source, not necessarily rot. Try rotating the pot a quarter turn every week or so, and make sure it's getting even light from all sides; if it's been tilting toward a window, that's probably your culprit. Root rot would show up as mushy spots or a foul smell when you water, so if the stem feels firm you're likely fine. Staking isn't really necessary for a barrel cactus, but if the tilt gets severe you could gently support it with a padded stake while you gradually reorient the light exposure.
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