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How to pot on seedlings

Updated: October 2026

Your seedling or cutting has sat in a small pot or module long enough that white roots show at the drainage holes, and the compost still holds together when you lift the plant with a finger under the rootball. That is the moment for potting on. It is not the day you first prick out bare roots from a seed tray, and not the day a 15 cm label looks tempting. This guide covers timing, how wide the next pot should be, and the move itself with peat-free compost on a UK bench. Product ranks stay on the [nursery pots comparison](/hub/plant-accessories/nursery-pots).

Your seedling or cutting has sat in a small pot or module long enough that white roots show at the drainage holes, and the compost still holds together when you lift the plant with a finger under the rootball.

Our top picks

Happy Pots Happy Pots (15 cm, 5)

Best overall

Happy Pots Happy Pots (15 cm, 5)
8.7/10about £10.49
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Happy Pots Happy Pots (7.5 cm, 10)

Alternative

Happy Pots Happy Pots (7.5 cm, 10)
8.1/10about £9.99
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Muzhira Muzhira (6 cm, 10)

Best value

Muzhira Muzhira (6 cm, 10)
8.4/10about £6.64
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On this page
  1. 1.When the plant is ready
  2. 2.One step, not a leap
  3. 3.How to move the plant
  4. 4.After you have potted on
  5. 5.When to move, and when to wait

When the plant is ready

Roots at the base of a cutting pot are the Gardeners' World signal that the plant can move on its own. For module-raised seedlings, RHS plug guidance says the plug should hold together when you push a pencil through the hole. If the compost falls apart, you waited too long or the mix was too loose. Hold seedlings by the seed leaves, not the stem. Garden Organic is explicit about that, because a bruised stem is harder to fix than a torn leaf. Water an hour before you move the plant so the rootball slides. Clear PET, mostly reviewed here for orchids, lets you see root colour without lifting. Pricking out bare seedlings from a tray is a different job. This page is the second move, when a rootball already exists.

One step, not a leap

RHS overpotting advice puts the next pot about 2.5–5 cm wider than the old one, and not much deeper. The same few centimetres appear in RHS guidance for pots under 25 cm. A worked Gardeners' World cutting moves from 9 cm to 11 cm. A 7.5 cm Happy Pots line into a 15 cm Happy Pots or Whitefurze pot is a 7.5 cm jump, wider than one step. If those are your only sizes, buy an intermediate 10 or 11 cm pot, or accept wet unused compost around a small rootball. The RHS remedy is to water only when the outer compost is drying, or to move the plant back to a pot just larger than the rootball. Tomatoes are the depth exception. Gardeners' World and Which? describe planting them deeper so the stem can root. Softwood cuttings stay at the same depth as before. Do not deep-plant every species because a tomato note said so.
Happy Pots Happy Pots (15 cm, 5)

Testsieger

Happy Pots Happy Pots (15 cm, 5)
8.7/10about £10.49
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How to move the plant

Prepare the new pot first. On Whitefurze, and on some clear KAHEIGN sizes, punch any closed membrane before compost goes in. RHS says not to cover small holes with crocks. Use peat-free multipurpose for a short stay, or a peat-free loam-based mix if the plant will live in the pot for months. Leave about a centimetre below the rim, as Garden Organic suggests. Match the old compost level, unless you are burying tomato stem on purpose. Firm gently and water with a fine rose. If a saucer came in the box, empty it. Most nursery rows here ship without one. Invert the old pot, spread your fingers across the compost, tap the rim, and slide. Do not pull the stem. Tease outer roots only if the plant is rootbound. Little root mesh means you should wait.

After you have potted on

Keep the plant in good light, out of harsh midday sun, for a few days. Moist is enough. An oversized pot dries slowly and rots faster if you water on the old schedule. When roots reach the holes again, step up a few centimetres. A start in a 6 cm ten-pack points next at 7.5 cm or 10 cm, not at the 15 cm top pick, until an intermediate pot is full. Cardboard plant-out pots go into the soil with the seedling. Hole checks still apply until that day. Materials are on plastic or fibre plant pots.

When to move, and when to wait

If roots show at the base and the plug lifts cleanly, move the plant into a pot about 2.5–5 cm wider, at the same compost level unless it is a tomato you mean to bury deeper. If the only larger pot you own is a full size-band jump, buy an intermediate pot or water only when the outer compost is drying. If the new base is still a membrane, punch it before you fill. If the compost falls apart in your hand, wait. The plant is not ready for this step.

Common questions

When is a seedling ready to pot on?
When roots show at the base, or the plug holds together and lifts cleanly after a gentle water. If the compost falls apart, it is not ready.
How much wider should the next pot be?
About 2.5–5 cm wider than the old rim, and not much deeper. A double jump only works if you accept careful watering of the unused compost.
Can I move a 7.5 cm seedling straight into a 15 cm pot?
You can, but that jump is wider than RHS one-step advice. Buy an intermediate size, or water only when the outer compost is drying.
What compost should I use in the UK?
Peat-free multipurpose for a short stay in the pot. A peat-free loam-based mix for longer container life, following RHS container advice.
What if the new pot’s holes are still closed?
Punch membranes before filling. Do not sow or pot on into a closed base, and do not cover the hole with crocks.
How is potting on a cutting different from pricking out a tray?
Potting on moves an existing rootball into the next size. Pricking out separates bare seedlings from a dense tray into their first pots.

Related pages

Nursery pots buying guide

Pots for seedlings

Nursery pots

Best nursery pots in 2026: top pick and best value

Plastic or fibre plant pots: reuse or plant them out

Sources

Public UK sources used for this comparison. Shelf prices, stars and review counts are the amazon.co.uk figures captured for these eleven listings. Last checked 22 October 2026.

  1. RHS: Growing plants in containers (retrieved 22 October 2026)
  2. RHS: How to plant up a container (retrieved 22 October 2026)
  3. RHS: Retail peat-free from 2026 (retrieved 22 October 2026)
  4. GOV.UK: Simpler recycling in England (retrieved 22 October 2026)
  5. HTA: Explanation of RAM for members (retrieved 22 October 2026)
  6. RHS: How to go plastic-free in your garden (retrieved 22 October 2026)
  7. West Sussex: Plant pots (retrieved 22 October 2026)
  8. Plant pot sizes: a UK guide (retrieved 22 October 2026)
  9. Consumer Rights Act 2015 (retrieved 22 October 2026)