Tomato planter

What the planter shows

Tomatoes can't take frost, so the planter never puts one outside before your area's typical last frost, and never before May. It counts roughly eight weeks from sowing to a young plant that's ready to go out. If that happens while frost is still likely where you live, the plant waits indoors and the planter tells you to pot it on. From planting out, it allows about eight weeks to the first fruit, then shows how much picking time is left before the first autumn frost.

Pot size matters as much as timing. Each plant wants at least 20 litres of compost, and the cutaway pot shows why: in a small pot the roots hit the wall and start circling (gardeners call that pot-bound). A standard growbag shared between two plants works out at less than that for each one, which is why the planter flags it.

The frost dates are long-term regional averages, not a forecast, so a cold spring can run a fortnight late. Keep some fleece handy and check the forecast before tender plants go out. For exact frost dates in your region, use the frost date checker.

Frequently asked questions

How big a pot does a tomato plant need?

At least 20 litres of compost per plant, which is a pot about 30cm across or larger. Bigger pots hold more water and are easier to look after. In a smaller pot the roots soon reach the wall and start circling, and the plant dries out fast.

When can tomatoes go outside in the UK?

Only once your area's typical last frost has passed, and not before May: from early May in the mildest areas to late May in northern Scotland. Many gardeners wait until nights stay above 10°C, which in much of the UK means late May or early June, so harden plants off for a couple of weeks and keep fleece handy.

How many tomato plants can go in a growbag?

Two. A standard growbag holds about 35 litres, so each plant gets about 17.5 litres, a little under the 20 litres a tomato likes. They still crop, but they dry out quickly, so water them often or cut bottomless pots into the top to give the roots more depth.

How long from sowing to the first ripe tomato?

About 8 weeks from sowing to a young plant ready to go out, then about 8 weeks from planting out to the first ripe fruit: roughly four months in all, and longer if frost keeps the plant indoors.