Full-sized green tomatoes sitting there week after week is maddening. The usual explanation is temperature — tomatoes ripen in a fairly narrow band, and both cool weather and extreme heat bring the process to a halt.
✅ Quick Answer
- Is this usually serious?
- Not at all. The fruit is fine. It’s a waiting game, with a few things you can do to help.
- Most common causes
- Temperatures too cool (below roughly 15°C) — ripening stalls
- Temperatures too hot (above roughly 30–32°C) — red pigment production stops
- Large-fruited varieties that simply take longer
- Too much nitrogen keeping the plant in leafy growth mode
- Too many fruit on the plant at once
- First thing to check
- What have your daytime temperatures been doing for the last two weeks?
- What NOT to do
- Don’t strip the leaves off to ‘let the sun in’. Sunlight doesn’t ripen tomatoes — it sunburns them.
👁 Look At Your Plant
Work through these before you decide what’s happening. Each one narrows it down.
- Has the fruit reached full size and gone slightly glossy? That’s mature green, and it will ripen.
- Are the fruit still small and dull? They aren’t ready yet, full stop.
- Has it been consistently above 30°C? Heat blocks lycopene, so fruit sits green or turns yellow-orange.
- Is it late in the season with cool nights? Ripening slows dramatically.
- Is the plant enormous and leafy with modest fruit? Suspect too much nitrogen.
- Is one plant carrying dozens of fruit? They ripen in sequence, not all at once.
Most Likely Causes
Temperature outside the ripening range
Tomatoes ripen best roughly between 18°C and 27°C. Below about 15°C the process crawls. Above about 30°C the plant stops producing lycopene, the pigment that makes tomatoes red, which is why heatwave tomatoes often stay green or ripen to a patchy orange.
Variety and days to maturity
Beefsteak and large heirloom varieties can take 80–90 days from transplant. Cherry types are far faster. If you planted late, the maths may simply be against you.
Excess nitrogen
A heavily fed plant prioritises leaves and stems. You get a magnificent green monster with fruit that sits there indefinitely.
Heavy fruit load
The plant can only funnel so much energy into ripening. A truss-heavy plant ripens slowly and in waves.
🔧 What To Do Now
- Be patient during heat. Ripening resumes when temperatures fall back into range.
- Provide afternoon shade during heatwaves so the plant stays in the ripening zone longer.
- Switch to a low-nitrogen, higher-potassium tomato fertiliser.
- Pick fruit at first blush and finish ripening indoors — flavour is barely affected once colour has started.
- Late in the season, remove new flowers and small fruit so the plant concentrates on what it can finish.
- Ripen picked green fruit in a paper bag with a banana or apple; the ethylene speeds it along.
❌ What NOT To Do
- Don’t defoliate the plant. Leaves make the sugars that ripen fruit and shield it from sunscald.
- Don’t leave fruit out in direct sun on a windowsill to ripen — warm shade works better.
- Don’t keep feeding high-nitrogen fertiliser hoping to speed things up.
- Don’t throw away end-of-season green tomatoes. Chutney exists for a reason.
💚 Can The Plant Recover?
Nothing to recover from — the fruit is fine. Expect ripening within one to three weeks once temperatures are in range. At the end of the season, pick everything mature-green before the first cold snap and ripen it indoors.
Filed under Tomato Fruit Problems. General gardening information — climate, soil, variety and local pests vary, so see our disclaimer.