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Repotting

Also known as Potting on, Potting up, Transplanting container plants

Growing know-howDepends
Three freshly repotted plants Photo: User:SB_Johnny · CC BY-SA 3.0

In short

Repotting gives a container plant fresh mix and, when needed, a little more room. Do it when roots have filled the pot, ideally as the plant starts active growth, and move up only one pot size. Large plants you want to keep at their current size can be root-pruned and returned to the same pot.

How it looks

A plant is ready for repotting when roots circle the inside of the pot or grow out of the drainage holes, the root ball is a dense mass with little visible mix, the mix dries out very quickly, or the plant wilts soon after watering. Slide the plant out of its pot to check: a healthy root ball holds together and shows white or light-coloured roots.

Signs

Needing water far more often than before, roots on the surface or through the drainage holes, stunted growth despite regular feeding, and a pot that tips over because the plant has become top-heavy.

What favours it

Fast-growing plants may need repotting every year; slow growers every 2–3 years; the RHS notes every three to five years suits many plants. Repotting when growth is slow (cool or dark periods) leaves fresh mix wet for longer and slows recovery.

Prevention

  • Repot in spring or early summer, as the plant starts active growth; avoid the plant's slow or resting period.
  • Choose a pot only about 2.5–5 cm (1–2 in) larger with drainage holes.
  • Use fresh, free-draining potting mix suited to the plant rather than garden soil.
  • Clean and disinfect reused pots before use.
  • Leave about 2.5 cm (1 in) between the mix surface and the rim so there is room to water.

Treatment

Start with the first step and move down only if the problem persists.

  1. Water the plant an hour or so before repotting so the root ball slides out more easily.
  2. Ease the plant out by supporting the base of the stems and tipping the pot; do not pull hard.
  3. Gently tease out circling roots; if very pot-bound, the RHS says up to about a quarter of the outer roots can be trimmed or scored.
  4. Put a layer of fresh mix in the new pot so the top of the root ball sits just below the rim, then fill around the sides, firming gently without packing.
  5. Water thoroughly until water runs from the drainage holes, then let excess drain away.
  6. For large plants you want to keep at their current size, Penn State suggests trimming the outer section of roots, returning the root ball to the same pot with some fresh mix, and cutting back some top growth.

Pros and cons

Pros

  • Fresh mix restores drainage and aeration and relieves a cramped root system.
  • A chance to inspect roots for rot or pests such as root mealybugs.

Cons

  • Root disturbance stresses the plant; some leaf drop or a pause in growth is common afterwards.
  • Repotting into too large a pot keeps the mix wet and risks root rot.

Look-alikes

Underwatering
A pot-bound plant dries out fast and looks thirsty; if watering more often is not enough, check the roots.
Root mealybugs
White, cottony patches on roots found during repotting are pests, not healthy root tips.

Typical uses

All container plants; orchids and other epiphytes need very porous, lumpy media.

Sources

  1. How to repot a plant — RHS
  2. Indoor Plants – Transplanting & Repotting — Clemson Cooperative Extension HGIC
  3. Repotting Houseplants — Penn State Extension
  4. Potting and Repotting Indoor Plants — University of Maryland Extension
  5. Houseplant Care — University of Wisconsin–Madison Extension

Written in our own words from these sources. Check a product label before using any treatment.