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Repotting Into Bigger Pots: One Size Up, Not Three

Go up one or two inches in diameter, never more. The signs a plant needs repotting, the right season, and why a huge pot sets it back.

By Salma 2 min read Save to Pinterest — opens Pinterest in a new tab
Empty terracotta and plastic pots beside a seedling in a heap of compost
Photo: Ylanite, Pixabay Content License, via Pixabay
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Repotting goes wrong in one direction: too big. One or two inches up is right, and the huge pot that looks generous is the thing that rots the roots.

Does it actually need repotting?

signmeaning
Roots out of the drainage holesYes
Roots circling the surfaceYes
Water runs straight throughYes — compost has shrunk or roots fill the pot
Dries out within a dayYes
Growth stalled despite feedingProbably
Pot tipping overYes
Just looks big for the potNot necessarily — check the roots

Lift the plant out and look. A solid mat with little visible compost is ready; loose compost at the edges is not.

Sizing the new pot

current potnew pot
4 in5–6 in
6 in7–8 in
8 in10 in
10 in12 in
12 in++2–3 in, or top-dress instead

Over-potting is the most common cause of root rot

Compost the roots cannot reach stays saturated, loses oxygen and goes stagnant. The plant then also spends a season filling the pot instead of flowering. A slightly tight pot is the better error.

The process

  1. Water the plant a few hours beforehand so the root ball holds together
  2. Have the new compost ready and lightly moist
  3. Slide the plant out, supporting the base — do not pull by the stem
  4. Tease the outer roots loose, and cut through any tight spirals with a clean knife
  5. Trim dead or mushy roots back to healthy tissue
  6. Add compost to the new pot so the plant sits at the same depth as before
  7. Backfill around the sides, firming lightly — no need to compact it
  8. Water thoroughly once, then leave it
  9. No feed for three or four weeks — fresh compost already contains nutrients

Aftercare

  • Bright indirect light, not full sun, for two weeks
  • Water only when the top inch dries
  • Expect a pause in growth; this is normal
  • Do not repot again to fix a sulking plant — that compounds it

Common questions

How much bigger should the new pot be?

One to two inches larger in diameter for a small plant, two to three for anything over about ten inches. Jumping several sizes is the commonest repotting mistake: the roots cannot occupy the extra compost, so it stays wet, goes stagnant and causes root rot, and the plant puts its energy into filling the pot rather than into leaves or flowers. A plant in a slightly tight pot almost always does better than one swimming in a huge one.

How do I know a plant needs repotting?

Roots emerging from the drainage holes or circling visibly on the surface, water running straight through without wetting the compost, the plant drying out within a day of watering, growth that has stalled despite feeding, or a pot that tips over because the plant has outgrown it. Lift the plant out and look — a solid mat of roots with little compost visible means it is ready, while loose compost and room at the edges means it is not.

When is the best time to repot?

Early spring, as growth starts, for most plants — the plant then has a full season to establish into the new compost. Repotting in autumn or winter leaves roots sitting in damp unused compost through the dormant period, which is when rot happens. The exceptions are plants in genuine trouble, where a root problem or collapsed compost justifies repotting at any time of year, and spring-flowering plants, which are better moved after they finish.

Should you loosen the roots when repotting?

Tease the outer roots free gently, and cut any that circle tightly. A root ball that has become a solid spiral keeps growing in that spiral even in new compost, so teasing the outside loose and slicing through a few of the circling roots with a clean knife encourages them outward. Do not shake off all the old compost or wash the roots unless you are dealing with disease — the fine feeder roots are easily destroyed and the plant pays for it in weeks of sulking.

Do I need to add drainage material at the bottom?

No, and it makes things slightly worse. The old practice of putting gravel or crocks in the base actually raises the saturated zone within the pot rather than improving drainage, because water perches above the change in texture. What matters is open drainage holes, a compost with enough structure, and not standing the pot in a saucer of water. A single crock over a large hole to stop compost washing out is fine.

Why is my plant worse after repotting?

Usually transplant shock, over-potting, or over-watering afterwards. A repotted plant has disturbed roots and needs a couple of weeks of stable conditions — bright indirect light, no feeding, water only when the top inch dries. If it was moved into a much bigger pot, the compost stays wet and the roots suffocate. Resist the urge to water more to help it; that is the main thing that turns a sulking plant into a dead one.

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