How to Ripen Green Tomatoes: Indoors, On the Vine & Before the First Frost

Every tomato grower knows the September arithmetic: trusses still loaded with green fruit, nights slipping towards single figures, and a first frost somewhere on the calendar. The instinct is to line every last tomato up on a sunny windowsill and hope. Here is the better news — ripening has almost nothing to do with sunshine, most of your green fruit can still turn red indoors, and the ones that never will make the best chutney of the year.

This guide explains which green tomatoes will ripen and which won't, how to speed them up with nothing more exotic than a banana, and how to squeeze the last weeks out of plants still standing. It pairs naturally with our guide to harvesting and storing your produce — this is the tomato-shaped chapter that deserves its own page.

• What ripens any full-sized, glossy fruit — even completely green
• Best spot 18–21 °C indoors; darkness is fine, sunlight unnecessary
• Speed trick a ripe banana in the bag or drawer (ethylene)
• Deadline pick everything before the first frost or sustained nights below 5 °C

Warmth ripens tomatoes — not sunlight

A tomato turns red through ripening chemistry triggered by ethylene, the gas fruit produces as it matures, and driven along by temperature. Light plays no meaningful part once the fruit is off the plant: commercial tomatoes ripen in the dark, and yours will too. The sunny windowsill is actually one of the worse spots — September sun through glass can overheat and scald fruit while the room's night chill stalls it again.

What green tomatoes want is steady warmth between 18 and 21 °C. Warmer than 25 °C and the red pigment lycopene develops poorly, leaving fruit orange and patchy; colder than about 12 °C and ripening slows to a crawl, while the fridge (below 10 °C) damages flavour permanently. A kitchen cupboard, a drawer, a cardboard box in the spare room — all beat the windowsill.

Which fruit will make it — and which never will

The dividing line is a stage growers call "mature green": the fruit is full-sized for its variety with a glossy skin, often paling from deep green towards a whitish or faintly blushing shoulder. Inside, the seeds are fully formed and cushioned in gel. Fruit at this stage ripens off the vine with no help beyond warmth. Immature fruit — small, dark, matte and rock-hard — has no engine to finish the job and belongs in the chutney pan.

One warning before you bring anything indoors: fruit from plants hit by late blight — brown-blotched stems, collapsing leaves — will not ripen, only rot, and can take a whole trayful with it. Learn the symptoms in our plant diseases guide and keep suspect fruit strictly separate.

The drawer-and-banana method, step by step

1. Pick dry, clean and unblemished Harvest on a dry day, leaving the little green calyx on. Split, bruised or spotted fruit goes to the kitchen today, not into storage.
2. Sort into ripe-soon and ripe-later Anything already blushing sits in the fruit bowl for this week. Mature green fruit goes into the ripening tray; immature fruit becomes chutney.
3. Lay them out in a single layer A shallow box, tray or drawer lined with newspaper, fruit not quite touching. Stacked tomatoes hide the one going bad underneath.
4. Add a banana and close the lid A ripe banana or apple leaks ethylene and can halve the wait. Loosely closed keeps the gas in and still lets air move.
5. Check twice a week Lift out anything colouring up, and evict anything soft or weeping immediately. Expect days for blushing fruit, one to three weeks for mature green.

Still on the vine? Push the plant to finish

While the weather holds, you can tilt a standing plant's effort towards the fruit it already carries. Pinch out the growing tip and any flowers now — from mid-September a flower has no realistic chance of becoming a ripe tomato, since the journey takes six weeks or more. Ease off watering and stop feeding; mild stress nudges the plant from growing towards ripening. Strip the leaves shading each truss so air moves around the fruit (and blight pressure drops), and throw fleece over everything on cold nights.

When frost is finally forecast, one old allotment trick beats picking fruit one by one: cut or pull the entire plant, shake off the soil, and hang it upside down in a frost-free shed or garage. The vine keeps feeding its fruit as it dries, and tomatoes ripen on the hanging plant for weeks. It looks eccentric and works beautifully.

Green tomatoes on purpose: the kitchen consolation

The immature pile is not a failure — green tomato chutney has converted more gardeners than any ripening trick, and firm green slices, crumbed and fried, are a small end-of-season feast. Cooking also deals with the tomatine that makes raw green tomatoes hard on some stomachs in quantity. And from your best, fully ripened fruit, consider one last job: scoop and dry some seeds for next year — our seed saving guide covers the fermentation trick that keeps tomato seed viable for years.

Common mistakes

• Ripening on a sunny windowsill. Heat spikes, night chill and scald — a cupboard at room temperature is faster and kinder.
• Refrigerating green fruit. Below 10 °C the ripening machinery and the flavour both break down for good.
• Stacking fruit deep. One rotting tomato at the bottom of a heap quietly ruins the lot.
• Trying to ripen blighted fruit. It rots, it spreads, it wins. Bin or burn, never compost.
• Waiting for frost "one more week". A single icy night turns every remaining tomato to mush. Pick on the forecast, not the calendar.

Frequently asked questions

Do green tomatoes ripen in the dark?
Yes — happily. Ripening runs on ethylene and warmth, not light. A dark drawer at 18–21 °C outperforms any windowsill.

How long do green tomatoes take to ripen indoors?
Blushing fruit turns in three to seven days. Mature green fruit needs one to three weeks depending on warmth. Anything unchanged after three weeks was immature — chutney it.

Can you eat green tomatoes raw?
A few slices won't hurt most people, but unripe fruit contains tomatine, which can upset the stomach in quantity. Cooking breaks it down — which is one more argument for chutney and for frying them.

Should I leave tomatoes on the vine as long as possible?
For flavour, vine-ripening wins while days stay mild. Once nights sit below 10 °C, indoor warmth ripens fruit faster and more evenly than a cold garden — and one frost ends the debate entirely.

Once the last vine is cleared, the bed itself is an opportunity: sow a green manure to feed next year's soil, tuck in some winter lettuce from the September sowing collection, and — while you're at it — start next summer's scent with our new guide to the heirloom sweet pea 'Painted Lady', which loves an October sowing. For next year's crop, browse all tomato varieties and the wider Solanum lycopersicum range, check the vegetable sowing calendar for timings, explore the full vegetable seed range, or dig into the rest of our growing guides — starting with how to grow vegetables from seed.