Repotting: when it is really needed (rarely) and how not to do harm
People repot far more often than necessary, almost always at the wrong moment and into too large a pot. How to tell when a plant is really asking for it, and the right way to avoid breaking roots.
People repot far more often than they need to. There is an idea that repotting is "giving the plant more", an act of care — when in fact it is a stress that should be done only when it is genuinely needed, which is rarely. A plant just bought, a plant that has just travelled, a plant that is struggling: none of these should be repotted. You repot a healthy plant, in active growth, that has actually filled its pot.
How to tell whether it is really asking
The reliable signal is roots coming out of the drainage holes, or surfacing and circling into a tight spiral when you gently slide the plant out of the pot. If you slide it out and still see plenty of substrate and few roots, it is not time: put everything back as it was. A plant that "grows slowly" almost never needs a bigger pot — it needs more light.
The mistake of the oversized pot
The temptation is to move to a much roomier pot "so it lasts longer". It backfires: all that substrate around few roots stays wet for a long time after every watering, and permanently damp substrate with no roots to drain it is exactly the condition in which roots rot. You go up one size only: two or three centimetres more in diameter, no more.
The right time of year
You repot in spring or early summer, when the plant is in its growing phase and rebuilds roots quickly. Repotting in autumn or winter, with the plant slowed down, means leaving it wounded and without the energy to heal — disturbed roots in cold damp substrate are an invitation to rot.
The right handling, so you do no damage
Water the plant the day before: a slightly damp root ball slides out whole, a dry one crumbles and tears the roots. Slide the plant out without pulling it by the stem — turn it over and guide it. Do not "tease out" a healthy root ball with your hands: leave it as it is and set it in the new pot. Add fresh substrate around it, pressing just enough to close the big air pockets but without compacting. The collar — where the stem enters the soil — stays at the same height as before: burying it deeper rots the base.
After repotting, treat the plant like one that has just arrived: indirect light, slightly higher humidity, and a light first watering. No fertiliser for three or four weeks, long enough for the cut roots to seal: feeding wounded roots burns them. If you had to cut rotten roots away during the job, keep the substrate barely damp, never soaked, until you see a new leaf — the signal that the plant has started working again below.