How do I know if my cactus needs repotting?

When was the last time you actually took it out of the pot? Root-bound is the obvious one, but what people miss is that cacti can stay in the same soil for years and actually prefer it - repotting too often is way more common than waiting too long. Check if water runs straight through without soaking in, or if the plant's just stopped growing entirely despite good light. If roots are circling the bottom or poking out drainage holes, yeah, time to move up a size, but honestly most cacti are happier staying put unless they're visibly suffering.

The tricky part people don't mention enough is that cacti genuinely hate being repotted. They'd rather stay put for years, and you can actually stunt their growth or stress them out by moving them too soon. So the real question isn't just "is it root-bound" but "is it suffering enough that the repotting won't harm it more than staying put."

Beyond the obvious signs like roots circling the soil or water running straight through, pay attention to whether the cactus itself is thriving. If it's growing steadily, holding its color, and you're watering it successfully in its current pot, leave it alone. The only time you really need to act is if growth has completely stalled, the soil legitimately won't retain any moisture even right after watering, or you can see the plant tilting because the root system can't support its weight anymore. Even then, repot during the growing season (spring or early summer), not in winter when cacti are dormant.

One thing that helped me was realizing that "outgrowing" a pot doesn't mean the same thing for cacti as it does for other plants. A cactus in a 4-inch pot might live contentedly for five years. Check it out once a year just to know what's going on inside, but unless something's actually wrong, resist the urge to refresh everything.

Best indicator is actually weight - pick up the pot and see if it feels unusually light a few days after watering, since soil that's compacted and root-bound dries out way faster than fresh cactus mix. The folks above are right that cacti hate being disturbed, but also remember that repotting in the wrong season (like winter dormancy) stresses them out even more, so spring is your window. If roots are genuinely spiraling or poking out, yeah do it, but otherwise you can honestly leave them alone for three or four years without issues.