Why Won't My Tomatoes Ripen?

Green tomatoes hanging on the plant are almost never a fault — they just need warmth and time. Tomatoes ripen slowly in cool weather and low light, so a chilly British summer or a late-set truss simply takes longer. As the season winds down, you can nudge them along on the plant, and anything still green by the first frosts will happily ripen indoors.

If you want the full method, see our guide to growing tomatoes.

Ranked causes and fixes

Most stalled tomatoes come down to one of these three, in roughly this order of likelihood.

1. Cool weather and low light. This is the big one in the UK. Tomatoes need a steady run of warm days to ripen, and they slow right down below about 16°C. A grey, cool spell in August or September can leave a whole truss sitting green for weeks. There's no quick fix for the weather, but patience usually wins — keep the plant healthy and the fruit will colour up once warmth returns. Outdoor plants in a cold, shady spot suffer most; a warm, sheltered, south-facing wall makes a real difference next year.

2. Too much leaf shading the fruit. A plant that's all foliage puts its energy into leaves, not ripening, and dense growth shades the trusses from what light there is. Thin out the leaves around ripening fruit (more on this below) so light and warmth reach them.

3. Too late in the season. If the fruit only set in late summer, it may simply have run out of warm weeks. Late trusses often won't ripen outdoors before the cold arrives — and that's fine, because you can finish them off indoors rather than losing them to frost.

Helping them ripen on the plant

From late August onwards, you can push the plant to focus on the fruit it already has rather than making new growth.

• Remove the lower and shading leaves. Take off leaves below the lowest ripening truss, and any thick foliage shading the fruit, so light and air get to them. Don't strip the plant bare — it still needs some leaves to work — but opening it up helps.
• Stop the plant. On cordon (indeterminate) tomatoes, pinch out the growing tip two leaves above the top truss in late summer. This is called "stopping": the plant stops trying to grow taller and ripens what it's carrying. Don't do this to bush (determinate) varieties, which crop all at once anyway.
• Ease back on water. Slightly reducing watering as the season ends concentrates the fruit and can nudge ripening along. Don't let plants wilt or dry out hard, though — sudden swings cause splitting tomatoes and stress.

Ripening green tomatoes indoors

When frost is on the way, harvest every fruit. Ripe ones eat now; green and part-coloured ones ripen indoors with one easy trick.

The banana or apple trick. Put the green tomatoes in a bowl or a paper bag with a ripe banana or apple. That fruit gives off ethylene, the natural gas that triggers ripening, and over one to two weeks your tomatoes turn red. Keep them somewhere warm-ish (a kitchen worktop, not a cold shed) and out of direct sun, and check every few days, removing any that soften or spoil. A sunny windowsill works too, just more slowly. Avoid the fridge — cold stalls ripening and dulls the flavour.

Use the truly green ones for chutney. Hard, fully green tomatoes that won't blush are perfect for green tomato chutney — a classic British way to use the end-of-season glut. Nothing need go to waste.

That's it: warmth and time on the plant, an open canopy and a stopped tip to focus the crop, and a banana in a bag for the stragglers. For everything from sowing to harvest, head back to the tomato growing guide, or browse more fixes in problem solving.

PS — green right up to the first frost is normal in a cool UK summer. Pick them, bag them with a banana, and you'll still be eating your own tomatoes well into autumn.