The humble small pot does one of the most important jobs in raising your own vegetables — giving pricked-out and potted-on seedlings the room they need to build strong roots before planting out. Here is how to use them well in a UK setup.
Last updated 4 July 2026
Small pots are one part of a wider propagation setup — for the full picture see our guide to propagation boxes and seed starting for UK vegetable growing.
Small pots rarely make anyone's "must-have gadget" list, but they quietly do essential work in raising your own vegetables. Between sowing and planting out sits a stage that decides how strong your plants are: pricking out seedlings from a seed tray and potting them on into their own small pots so each builds a proper root system. Get this stage right and you plant out sturdy, well-rooted plants; get it wrong and you plant out weak, leggy ones. This guide is about using small pots well for that job.
Pricking Out: Giving Seedlings Their Own Space
When seedlings sown thickly in a tray have their first pair of true leaves, they need more room. Pricking out means lifting each one gently — by a leaf, never the fragile stem — and settling it into its own small pot of fresh compost. This is where a small pot earns its keep: it gives one seedling the light, air and root room it cannot get crowded in a tray.
Grower's note: Always handle a seedling by a seed leaf, not the stem. The Royal Horticultural Society's standard pricking-out advice is that a crushed stem kills the seedling, whereas a damaged leaf can be replaced. Water the tray an hour before, and the little rootballs lift out far more cleanly.
Potting On: Matching Pot to Root
As a plant grows, it may need moving up a pot size — potting on — before it is ready to plant out. The key is to increase pot size gradually. A tomato seedling jumped straight into a large pot sits in cold, wet compost its small roots cannot use, which invites rot. Moving up one modest size at a time keeps the compost warm and the roots active. Tomatoes are the classic crop for this staged approach, and our guide to growing tomatoes in the UK covers the whole journey from sowing to cropping.
Choosing and Reusing Small Pots
For UK vegetable growing, a stack of small 7–9cm pots covers most pricking-out and potting-on needs. Rigid plastic pots reused season after season are more sustainable and more practical than single-use biodegradable ones for this stage, because they hold their shape and let you knock a rootball out cleanly. Wash them between uses to reduce the risk of damping-off disease carrying over. Lightweight pots also matter if you are shuffling trays of seedlings on and off a windowsill or in and out of a cold frame to harden off.
Timing It With the UK Season
Potting on buys you time indoors while it is still too cold to plant out. In a UK spring that flexibility is valuable — a well-potted-on plant can wait safely for the weather rather than being rushed into cold soil. Knowing when it is genuinely safe to plant out matters just as much as the potting: our guide to when to plant tomatoes in the UK sets out the timing so your potted-on plants go out at the right moment.
Plan Your Entire Growing Season
Month-by-month sowing schedules, crop guides for every UK vegetable, companion planting charts, and harvest trackers — all calibrated for UK conditions.
Get the UK Garden Planner →For the trays, propagators and other kit that go alongside your small pots at the seed-starting stage, see our UK seed-starting tools guide.
Frequently Asked Questions
What size pots do I need for pricking out vegetable seedlings?
Small 7–9cm pots suit most pricking-out and early potting-on needs. Each pricked-out seedling goes into its own pot of fresh compost so it can build a strong root system with enough light and air, which crowded seed trays cannot provide.
How do I prick out seedlings without killing them?
Water the tray about an hour beforehand, then lift each seedling gently by a seed leaf — never the stem — and settle it into its own small pot. A crushed stem kills the seedling, whereas a damaged leaf can be replaced, so always hold by a leaf, as the RHS advises.
Should I move seedlings straight into a big pot?
No. Increase pot size gradually. A small seedling put straight into a large pot sits in cold, wet compost its roots cannot use, which encourages rot. Potting on one modest size at a time keeps the compost warm and the roots growing, especially with tomatoes.
Are reusable plastic pots better than biodegradable ones for potting on?
For pricking out and potting on, yes. Rigid plastic pots hold their shape, let you knock out a rootball cleanly, and last many seasons. Wash them between uses to reduce damping-off. Biodegradable pots are better saved for crops that resent root disturbance and are planted pot and all.
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