How to Ripen Green Tomatoes in the UK: Complete Guide

If you’ve been growing tomatoes throughout the summer, you’ll know how frustrating it can be when autumn arrives and your plants are still covered in green tomatoes.

You’ve spent months sowing seeds, potting on seedlings, watering, feeding and looking after your plants, only for the weather to turn colder before all the fruits have ripened.

It’s a familiar situation for gardeners across the UK.

Fortunately, there are several ways to encourage mature green tomatoes to ripen, even after they’ve been removed from the plant.

Whether you’re growing tomatoes in a greenhouse, polytunnel, raised bed or containers, understanding how the ripening process works can help you make the most of your harvest.

Here at Gardening with Ben, I always think it’s a shame to waste a crop after spending so much time growing it. When the growing season begins coming to an end, it’s worth checking every tomato plant and making the most of the remaining fruits.

In this complete guide, we’ll explore how to ripen green tomatoes in the UK, why tomatoes sometimes refuse to turn red, the best indoor ripening methods, whether bananas really help and what to do with green tomatoes before winter.

Why Are My Tomatoes Still Green?

Tomatoes need suitable growing conditions and time to reach their mature colour.

In the UK, ripening can slow considerably during late summer and autumn as temperatures fall and daylight decreases.

However, cool weather isn’t the only reason tomatoes remain green.

1. Temperatures Are Too Low

Tomatoes generally ripen most effectively at moderate temperatures.

As temperatures fall, the ripening process slows.

Cool autumn nights can delay colour development, particularly on outdoor plants.

2. Temperatures Are Too High

Surprisingly, excessive heat can also interfere with tomato ripening.

Very high greenhouse temperatures may slow the production of the pigments responsible for red colour.

This means tomatoes can remain green even during hot weather.

3. The Tomatoes Aren’t Mature Yet

A tomato needs to reach a sufficiently developed stage before it can ripen successfully.

Small, immature fruits may remain green even when moved indoors.

4. The Growing Season Is Ending

Shorter days and falling temperatures can slow plant growth.

Tomatoes that developed late in the season may not have enough time to ripen outdoors.

5. The Variety Takes Longer to Ripen

Some tomato varieties naturally mature later than others.

Large beefsteak tomatoes often take longer to develop than many cherry varieties.

6. The Plant Is Under Stress

Drought, waterlogging, disease and poor growing conditions can affect fruit development.

Healthy plants are generally better able to support a good harvest.

Can Green Tomatoes Ripen After Picking?

Yes, many green tomatoes can continue ripening after being picked.

Tomatoes are climacteric fruits, meaning they can continue the ripening process after harvest.

They respond to ethylene, a naturally occurring plant hormone involved in ripening.

However, there’s an important condition.

The tomatoes must be sufficiently mature.

A fully developed mature-green tomato may ripen successfully indoors.

A very small, immature green tomato may never develop its normal ripe colour or flavour.

This is why selecting the right tomatoes makes such a difference.

How to Tell Whether a Green Tomato Is Mature Enough to Ripen

Before bringing green tomatoes indoors, inspect them carefully.

Signs of a Mature Green Tomato

Look for:

• Fruit that has reached approximately its expected full size
• A firm, well-developed shape
• A change from very dark green to a lighter or more mature green appearance
• A slight pale or whitish colour at the blossom end in some varieties
• No significant disease or damage

These signs vary by variety.

Signs a Tomato May Be Too Immature

Very small, hard fruits that haven’t reached their expected size are less likely to ripen successfully.

Some may soften or change colour slightly but never develop good flavour.

The Breaker Stage

The breaker stage is when the first noticeable change from green to the mature colour appears.

For red tomatoes, this may be a faint pink, yellowish or reddish patch.

Tomatoes harvested at this stage generally ripen more reliably than completely green fruits.

Best Temperature for Ripening Green Tomatoes Indoors

Temperature is one of the most important factors.

For many tomato varieties, a room temperature of approximately 18–21°C is a useful target.

Tomatoes may ripen at somewhat cooler temperatures, but the process is usually slower.

Avoid placing tomatoes directly against radiators or other strong heat sources.

Excessive warmth can encourage softening, shrivelling and decay.

Do Tomatoes Need Sunlight to Ripen?

No.

Tomatoes don’t need direct sunlight once they have been picked to continue ripening.

The ripening process depends primarily on fruit maturity, temperature and ethylene.

Direct sunlight through a window can cause excessive heating.

A bright windowsill is not essential.

Method 1: Ripening Green Tomatoes in a Paper Bag

One of the simplest methods is to place mature green tomatoes inside a paper bag.

How to Do It

1. Select healthy, mature green tomatoes.
2. Check that they are dry and free from significant damage.
3. Place a few tomatoes into a paper bag.
4. Fold the top loosely rather than sealing it airtight.
5. Keep the bag at a suitable room temperature.
6. Check the tomatoes every day or two.
7. Remove ripe fruits promptly.

Why Does a Paper Bag Work?

Tomatoes naturally release ethylene.

A paper bag can help retain some of this gas around the fruit while still allowing limited airflow.

This may encourage ripening.

Important Tip

Don’t overcrowd the bag.

Inspect regularly because one rotting tomato can affect the others.

Method 2: Ripening Tomatoes with a Banana

You’ve probably heard that placing a banana with green tomatoes can help them ripen.

There is a scientific reason behind this advice.

Ripening bananas release ethylene gas.

This gas can help trigger or accelerate ripening in sufficiently mature tomatoes.

How to Use a Banana

1. Choose healthy, mature green tomatoes.
2. Place them inside a paper bag or ventilated container.
3. Add a ripening banana.
4. Keep the container at room temperature.
5. Inspect the tomatoes and banana regularly.
6. Remove any fruit that becomes overripe or begins decaying.

Does the Banana Have to Be Yellow?

A banana that is actively ripening generally releases more ethylene than a very unripe banana.

Will This Ripen Every Green Tomato?

No.

Ethylene cannot reliably turn very immature tomatoes into fully developed ripe fruits.

The method works best with tomatoes that have already reached physiological maturity.

Method 3: Ripening Tomatoes with an Apple

Apples also release ethylene.

A ripening apple can therefore be used in a similar way to a banana.

How to Use an Apple

Place a ripe apple with several mature green tomatoes inside a loosely closed paper bag.

Keep the bag at room temperature.

Inspect regularly.

Is an Apple Better Than a Banana?

Both can be useful.

The amount of ethylene released varies according to fruit variety and ripeness.

Neither method guarantees success with immature tomatoes.

Method 4: Ripening Tomatoes in a Cardboard Box

A cardboard box is useful when you have a larger harvest of green tomatoes.

Step 1: Choose a Suitable Box

Use a clean, dry cardboard box.

Step 2: Add a Protective Layer

Line the bottom with clean paper if desired.

Step 3: Arrange the Tomatoes

Place the tomatoes in a single layer where possible.

Avoid piling heavy fruits on top of one another.

Step 4: Separate Damaged Fruits

Only include healthy tomatoes.

Step 5: Keep at Room Temperature

Choose somewhere reasonably warm and dry with adequate ventilation.

Step 6: Check Regularly

Inspect the tomatoes every day or two.

Remove ripe fruits and discard any showing signs of decay.

Can You Add a Banana?

Yes.

A ripening banana or apple may help encourage colour development.

However, inspect the box regularly to prevent mould or rotting.

Method 5: Ripening Tomatoes on a Tray

For a small number of tomatoes, you may not need a bag or box at all.

Simply arrange mature green tomatoes on a clean tray.

Best Conditions

• Suitable room temperature
• Good airflow
• No direct intense sunlight
• No excessive moisture
• Regular inspection

This method is straightforward and allows you to see immediately when tomatoes begin changing colour.

Method 6: Bringing an Entire Tomato Plant Indoors

If you’re growing tomatoes in containers, you may be able to move the entire plant into a protected location before frost.

This can allow some fruits to continue developing.

When This Method Works Best

It’s most practical for:

• Compact bush tomatoes
• Patio tomatoes
• Small container-grown plants
• Healthy plants with developing fruits

How to Do It

Move the container into a bright, frost-free location.

Maintain appropriate watering.

Avoid placing it near strong heat sources.

Will All the Tomatoes Ripen?

Not necessarily.

Plants moved indoors may struggle with lower light levels.

Fruits that are already mature have the best chance of ripening.

Method 7: Hanging Tomato Plants Upside Down

Some gardeners remove entire tomato plants at the end of the season and hang them upside down in a frost-free location.

The idea is to allow remaining mature fruits to continue ripening while attached to the plant.

How to Try It

1. Select a healthy plant with mature green tomatoes.
2. Remove it before frost damages the crop.
3. Shake away loose soil carefully.
4. Hang it in a dry, frost-free, ventilated location.
5. Inspect the fruits regularly.

Does It Work?

Some mature tomatoes may continue ripening.

However, the method isn’t necessarily better than picking the fruits and ripening them separately.

It also takes up space and may introduce pests or decaying plant material indoors.

For most gardeners, harvesting mature green tomatoes and placing them in trays or boxes is more convenient.

Should You Leave Green Tomatoes on the Plant?

If the weather remains mild and the plant is healthy, leaving tomatoes attached is often the best option.

Fruits can continue receiving resources from the plant while they develop.

However, as temperatures fall, the benefits of leaving them outdoors decrease.

Leave Them on the Plant When:

• The weather is still mild.
• There is no immediate frost risk.
• The plant is healthy.
• Fruits are continuing to develop.
• The greenhouse or polytunnel provides suitable protection.

Harvest Them When:

• Frost is forecast.
• Temperatures are consistently too low for useful ripening.
• The plant is declining.
• Disease is threatening the fruits.
• The growing season has effectively finished.

What to Do with Green Tomatoes Before the First Frost

Tomato plants are vulnerable to frost.

If frost is forecast, act before the plants are damaged.

Step 1: Check the Weather Forecast

Pay attention to overnight temperatures.

Conditions can vary significantly between sheltered gardens and exposed allotments.

Step 2: Harvest Ripe Tomatoes

Pick all fruits that have reached their mature colour.

Step 3: Collect Mature Green Tomatoes

Select full-sized, healthy green fruits that have a reasonable chance of ripening indoors.

Step 4: Separate Immature Fruits

Very small green tomatoes may be better used in suitable cooked recipes rather than kept for ripening.

Step 5: Inspect for Disease

Discard tomatoes showing signs of serious rot or blight.

Step 6: Move Suitable Container Plants

Where practical, bring healthy container plants into frost-free conditions.

How to Ripen Green Tomatoes in a Greenhouse

Greenhouses can extend the growing season.

However, an unheated greenhouse can still become very cold during autumn.

Improve Ventilation

Good airflow helps reduce excessive humidity and condensation.

Maintain Suitable Watering

Avoid both severe drought and waterlogging.

Remove Diseased Material

Inspect leaves and fruits regularly.

Consider Temperature

Once nights become consistently cold, ripening may slow considerably.

Harvest Before Frost Damage

If an unheated greenhouse is likely to freeze, collect mature green fruits beforehand.

Should You Remove Tomato Leaves to Help Fruits Ripen?

Removing a limited number of leaves can sometimes improve airflow and expose fruit trusses.

However, removing large amounts of healthy foliage is not automatically beneficial.

Leaves produce energy through photosynthesis.

Excessive defoliation can reduce the plant’s ability to support developing fruits.

Which Leaves Should You Remove?

Consider removing:

• Dead leaves
• Diseased leaves
• Leaves touching wet soil
• Selected lower leaves where airflow is poor

Avoid stripping a healthy plant unnecessarily.

Should You Stop Tomato Plants in Late Summer?

Stopping a cordon tomato means removing the main growing tip.

This prevents the plant from continuing to produce new growth at the top.

During late summer, stopping outdoor cordon tomatoes can help focus the remaining growing season on existing fruits.

When Should You Stop Tomatoes?

Many UK gardeners stop outdoor cordon tomatoes during August, depending on local conditions and how many fruit trusses have developed.

Greenhouse tomatoes may continue growing for longer.

Should You Stop Bush Tomatoes?

Bush tomatoes generally don’t require the same routine stopping method.

Their growth habit is different.

Should You Remove Tomato Flowers in Autumn?

Late-season tomato flowers may not have enough time to develop into ripe fruits before winter.

Removing newly forming flowers can be reasonable when the growing season is nearly over.

However, this isn’t guaranteed to make existing fruits ripen dramatically faster.

Temperature and fruit maturity remain the most important factors.

How Long Do Green Tomatoes Take to Ripen Indoors?

Ripening time varies considerably.

A tomato that has already started changing colour may ripen within a few days.

A fully mature green tomato may take one to three weeks or sometimes longer.

Some tomatoes will not ripen successfully.

Factors Affecting Ripening Time

• Variety
• Fruit maturity
• Temperature
• Ethylene exposure
• Fruit health
• Storage conditions

Check fruits regularly rather than expecting them all to ripen together.

Why Are My Green Tomatoes Not Ripening Indoors?

If your tomatoes remain green, several factors may be responsible.

They’re Too Immature

This is one of the most common reasons.

The Room Is Too Cold

Cool temperatures slow the ripening process.

The Room Is Too Hot

Excessive heat can interfere with colour development and fruit quality.

The Tomatoes Are Diseased

Diseased fruits may rot before ripening.

The Variety Ripens to Another Colour

Not all tomatoes turn red.

Some varieties ripen yellow, orange, purple or green.

Check the expected mature colour of your variety.

Can Green Tomatoes Turn Red in the Fridge?

Refrigeration is not a good method for ripening green tomatoes.

Cold temperatures slow the ripening process and can affect flavour and texture.

For ripening, use suitable room-temperature conditions instead.

Once tomatoes are fully ripe, short-term refrigeration may help slow deterioration if necessary, although allowing them to return to room temperature before eating can improve flavour perception.

Can You Ripen Green Tomatoes in Direct Sunlight?

Direct sunlight isn’t required for picked tomatoes to ripen.

A sunny windowsill may become excessively hot, particularly behind glass.

This can encourage softening and uneven ripening.

A suitable room-temperature location away from strong direct sunlight is generally preferable.

Can You Eat Green Tomatoes?

Green tomatoes can be used in certain recipes, but there are important considerations.

Unripe tomatoes contain glycoalkaloids, including tomatine.

Levels generally decline as the fruit ripens.

Avoid eating large quantities of raw, unripe green tomatoes, particularly if they are very immature.

Use suitable recipes and moderate portions.

Also remember that some tomato varieties remain green when fully ripe.

These are different from immature green tomatoes.

Popular Uses for Green Tomatoes

• Green tomato chutney
• Pickles
• Cooked green tomato relish
• Fried green tomatoes
• Suitable preserves

Discard any fruit that is mouldy, rotten or showing serious disease symptoms.

Can You Freeze Green Tomatoes?

Yes, green tomatoes can be frozen for later cooking.

However, freezing changes their texture.

They won’t become fresh, firm, ripe tomatoes after thawing.

How to Freeze Green Tomatoes

1. Select sound fruits.
2. Wash them thoroughly.
3. Remove stems and damaged areas.
4. Cut into suitable pieces if required.
5. Pack into freezer-safe containers or bags.
6. Label and freeze.

Frozen tomatoes are best used in cooked dishes.

How to Prevent Too Many Green Tomatoes at the End of Summer

Although indoor ripening is useful, it’s even better to encourage tomatoes to mature during the growing season.

Choose Early-Maturing Varieties

Early varieties are particularly useful for outdoor growing in cooler parts of the UK.

Sow at the Right Time

Start seeds indoors during spring.

Avoid sowing too late for your intended growing method.

Provide Plenty of Light

Tomatoes need suitable light to develop healthy plants and fruits.

Maintain Consistent Watering

Irregular watering can stress plants and affect fruit quality.

Feed Appropriately

Use a suitable tomato fertiliser when flowering and fruiting begin.

Avoid excessive nitrogen.

Support and Prune Correctly

Manage cordon tomatoes appropriately.

Don’t remove side shoots routinely from bush varieties.

Protect from Cold

Use greenhouses, polytunnels or suitable outdoor protection where practical.

Monitor for Blight

Healthy plants are more likely to support fruits through to maturity.

Common Mistakes When Ripening Green Tomatoes

Picking Fruits Too Early

Very immature tomatoes may never ripen properly.

Storing Tomatoes in the Fridge

Cold temperatures slow ripening.

Using Too Much Heat

Placing tomatoes beside radiators can cause deterioration.

Leaving Rotten Fruits in the Box

Decay can spread to nearby fruits.

Sealing Tomatoes in Plastic Bags

Airtight bags can trap moisture and encourage mould.

Expecting Every Tomato to Turn Red

Some varieties ripen to other colours, and some immature fruits won’t ripen at all.

Forgetting to Check Them

Tomatoes can change quickly once ripening begins.

Inspect them regularly.

Frequently Asked Questions About Ripening Green Tomatoes

How Do You Ripen Green Tomatoes Quickly?

Place sufficiently mature green tomatoes at a suitable room temperature. A paper bag with a ripening banana or apple may help.

Will Green Tomatoes Ripen After Picking?

Yes, provided they have reached sufficient maturity.

Do Green Tomatoes Need Sunlight to Ripen?

No. Direct sunlight is unnecessary after harvesting.

Does Putting a Banana with Green Tomatoes Work?

It can help because ripening bananas release ethylene gas.

Can You Ripen Green Tomatoes in a Paper Bag?

Yes. Use a loosely closed paper bag and inspect the fruits regularly.

Can You Ripen Green Tomatoes in a Cardboard Box?

Yes. Arrange healthy fruits carefully and keep the box at a suitable temperature.

How Long Does It Take Green Tomatoes to Turn Red?

Some ripen within days, while others take several weeks.

What Temperature Is Best for Ripening Tomatoes?

Approximately 18–21°C is a useful target for many varieties.

Can You Ripen Green Tomatoes in the Fridge?

No. Refrigeration slows ripening and may affect quality.

Should You Pick Green Tomatoes Before Frost?

Yes. Harvest suitable mature fruits before frost damages them.

Can You Ripen Tomatoes on the Vine Indoors?

Some may continue ripening if a healthy plant is moved into suitable conditions, but results vary.

Should You Remove Tomato Leaves to Help Ripening?

Remove dead or diseased leaves as appropriate, but avoid excessive removal of healthy foliage.

Why Won’t My Tomatoes Turn Red?

They may be immature, too cold, too hot or a variety that ripens to another colour.

Can You Eat Green Tomatoes?

They can be used in suitable cooked recipes, but avoid consuming large amounts of raw, immature green tomatoes.

Can You Freeze Green Tomatoes?

Yes. They’re best used in cooked dishes after freezing.

What Should You Do with Green Tomatoes in October?

Harvest healthy, mature green fruits before frost and ripen them indoors. Use suitable remaining fruits for cooking or preserving.

Final Thoughts: Ripening Green Tomatoes Successfully in the UK

Having green tomatoes remaining on your plants at the end of summer doesn’t mean your growing season has been wasted.

Many mature green tomatoes can continue ripening indoors, giving you the opportunity to enjoy more of your homegrown harvest.

The key is choosing fruits that are sufficiently developed and keeping them at a suitable temperature.

Paper bags, cardboard boxes and simple trays can all work well.

Adding a ripening banana or apple may help because these fruits release ethylene gas.

However, remember that no method can guarantee ripening if the tomatoes are too immature.

As autumn approaches, keep an eye on the weather forecast and harvest suitable fruits before frost arrives.

With a little patience and care, you may still be enjoying delicious homegrown tomatoes long after the outdoor growing season has finished.

Keep smiling, keep shining, keep gardening with Ben!