Ripening Tomato Myths – Both on the Vine and in the Home

source: Gardening Myths



You have worked hard all spring and summer to get some fresh red tomatoes from the garden. Now you have all kinds of green tomatoes on the vine and hope that they get red before the frost hits. What can you do to speed up the ripening process? Should you remove some leaves and let more sun reach the fruit? Can you harvest them green and complete the ripening process inside?

Some people suggest putting a banana or apple in a bag with green tomatoes to ripen them – does this work?

Does fertilize or water affect ripening? Would a change in culture speed up the tomato ripening process? Let’s have a close look at the facts and help you bite into a red tomato.


Vine Ripened Tomatoes Taste Better

We have all eaten store bought tomatoes and they have very little flavor – that’s why we grow our own. This lack of flavor is blamed on the fact that store bought tomatoes are picked and shipped green.

Most people now believe that in order for tomatoes to taste good, they must be ripened on the vine.

What is a ripe tomato? It is hard to define, but it should have reached it’s full size and final color. The color could be red, yellow, black, purple and even green striped. Whatever color it is, it should be as intense as possible for the selected cultivar.

The idea that vine ripened tomatoes taste better is a myth – I’ll explain why below.

You can remove fruit that has reached something called the breaker point, ripen them inside, and they will taste as good as vine ripened tomatoes. In very hot weather, ripening inside at lower temperatures can actually produce a better tasting tomato.



Sun scald on a tomato, photo credit: Missouri Botanical Garden

Do Tomatoes Need Sun Light to Ripen?

The answer is no.

I think we associate the red color of tomatoes with the reddish color of the sun, and incorrectly assume that the sun plays a direct role in the ripening process. It doesn’t.

Therefore, removing leaves from the plant to expose the fruit will NOT speed up the ripening process. In fact it can slow down the process because ripening stops when temperatures get too high. Fruits exposed to direct sunlight can reach a temperature 20 degrees F higher than that of shaded fruits which is enough to stop ripening.

Direct sun exposure can also result in fruit with sun scald.


What is Mature Fruit?

The general population mostly considers a tomato mature when it is red and ready to eat. Botanists define maturity differently. A fruit is mature when the seeds have developed to a point where they will germinate. After all, the plant is producing fruit to make seeds, not to feed us. A tomato reaches the mature stage (ie viable seeds) when it is still green.


What is the Tomato Ripening Process?

Understanding the growing and ripening process provides good insight into how we can better ripen garden tomatoes. There are several stages in this process including, pollination, reaching the mature green stage, the breaker stage and finally, full ripeness.


Pollination

Pollination needs to happen to start the process. When flowers are not pollinated, bud drop happens and I have discussed this in What Causes Blossom Drop in Tomatoes?. Most tomatoes grown in North America stop setting fruit at about 85 F, but there are cultivars that set fruit at higher temperatures.



Tomato ripening stages, photo by Cantwell, Marita, UC Davis


Mature Green Stage

Once pollinated, the fruit starts to develop and enlarge in size. The seeds are also developing. Both the outside and inside of the fruit remains green and it can take 40 – 50 days to finish growing.

Tomato ripening stages, photo by Cantwell, Marita, UC Davis

As the fruit reaches the end of this stage, it starts producing a significant amount of ethylene, a natural hormone that initiates the ripening process.

At the end of this stage, the fruit stops growing in size and the outside color turns a pale green. The fruit and seeds are now mature.


The Breaker Stage

The fruit starts the ripening process a couple of days after reaching the mature green stage,. The exact timing of this depends on the variety, but generally its correlated with fruit size where cherry types go faster and large fruited ones take longer (personal communication with Jim Giovannoni).

Recent research indicates that the ripening process is triggered by epigenetics, which is a chemical process that alters the activity of DNA genes. Certain ripening genes are turned on by this process.

You can see the changes visually both on the skin and inside the fruit, both of which start turning a pinkish color.

The breaker stage is reached when the fruit has a definite pink coloration on 10 – 30% of the fruit.

An important change takes place in the stem of the fruit when it reaches the breaker stage. “A layer of cells form across the stem of the tomato, sealing it off from the main vine. When this occurs, there is nothing that can move from the plant into the fruit. The tomato can be harvested and ripened off the vine with no loss of flavor, quality or nutrition.”


Fully Ripe Stage

The fruit continues to produce more ethylene, which speeds up the ripening process, until the fruit is fully ripe. The process takes 2 to 7 days.


From Green to Ripe Stage


During the process of going from green to breaker to ripe, several changes take place in the fruit. Acidity, starch and firmness go down, while aroma, sugars, flavor and color go up. The process is affected mostly by the amount of ethylene and the temperature.


Tomato stages; breaker stage on the left, green immature stage on the right


Temperature Affects the Ripening Process

The ideal temperature for ripening is 68–77 F (20-25 C). Ripening slows down above and below this range. Extended periods of a few days outside of this range can stop the ripening process.

Above 85 F (30 C), the tomato will not produce lycopene and carotene, the pigments responsible for the ripe tomato color.

It is common for tomato plants to reach the mature green stage by mid-summer, when it’s very hot. When this happens, gardeners start complaining that their green fruit is just not ripening. It is all due to temperature.

Removing leaves makes the problem worse. Adding shade cloth can reduce the temperature and speed up ripening.

Refrigeration destroys the flavor.


Does Fertilizer or Water Affect the Ripening Process

Fertilizer and water affects the development process up to the mature green stage, but they don’t change the ripening process.


Harvest at Breaker Stage

When is the best time to harvest? The breaker stage.

After this point, the tomato is sealed off from the plant and no nutrients or sugars enter the fruit. There is no value in leaving it on the plant.

There are benefits for taking the fruit off. It is less likely to be damaged by insects, birds or the local chipmunk population. It also won’t split if you have a sudden heavy rain. In warm weather, taking it inside to a cooler spot can actually speed up the ripening process.

If a tomato is picked at or after the breaker stage it will ripen properly, and reach full flavor and full nutrition inside your home.

Light has no effect on the ripening process. Just keep them on your kitchen counter.

If you have too many tomatoes, store some in a cooler place to slow down the ripening process but keep the temperature above 50 F (10 C).


Recognizing the Mature Green and Breaker Stages

Tomato stages; breaker stage on the left, green immature stage on the right

The breaker stage is identified by looking closely at the outside skin. When it takes on a slight pinkish coloration, usually at the bottom of the fruit, it has reached breaker stage.

There is nothing wrong with leaving the fruit on the vine an extra day or two to be sure that this color change has taken place.

The mature green stage is much more difficult to detect. The best way to do this is to cut the fruit open and look at the seeds. The jelly that surrounds the seeds will be solid before the fruit reaches mature green and becomes more jelly like once mature. The seeds are typically smaller and whiter before maturation but once they have a gray or light brown color, they have a fully developed seed coat and are mature.

Cutting fruit open is not a great idea if you want to keep and ripen the fruit so you are limited to looking at the outside of the fruit, which can be tricky.

Fruit will have reached its maximum size when mature, but the size of fruit can vary on a single plant. A day or two before reaching mature green, the color changes from green to a light green (personal communication with Jim Giovannoni). To be honest, I have trouble seeing this difference.


Using Artificial Ethylene

You have probably heard about putting the green tomatoes in a box or bag along with a ripe apple or banana. The idea here is that these ripe fruits produce their own ethylene gas, which fills the container causing tomatoes to ripen quicker.

Ethylene is also used commercially to speed up ripening. Commercial tomatoes are usually picked at or before mature green and stored cool to suspend the ripening process. When they are required for market, they are warmed up and treated with ethylene, so that they are ripe by the time they reach the store.

Artificial ripening of tomatoes that have not reached the breaker stage results in poor eating-quality fruit. That is why people complain about store bought tomatoes.


Use a Banana or Apple to Ripen Tomatoes

ripen tomatoes in a box with a banana, photo credit Clean Soul kitchen

Does this work? Should you add a banana or apple to your tomatoes to speed up ripening?

It depends.

A ripe banana or apple will produce ethylene gas which can speed up the tomato ripening process in some cases.

The best option is to pick fruit at the breaker point and not use other fruit to ripen them. The reason for this is that too much ethylene speeds up the process too much, resulting in less flavorful tomatoes.

Will green tomatoes ripen with a banana or apple? If the fruit is very young and underdeveloped, it just won’t ripen no matter what you do. Fruit that is close to being mature green will ripen. What is the cutoff for this? I don’t know. What is clear is that if immature fruit does ripen, it will lack flavor and it will take quite some time to ripen, so it might not be worth the effort.

Some reports on social media claim that a banana works, and others say it doesn’t. This discrepancy is probably due to fruit being picked at different development stages. Pick it too early and it won’t work. Pick it at a more mature stage and it does work.

Not all fruit produces ethylene as it ripens, so this trick of ripening tomatoes won’t work with all fruit. For example, grapes won’t work.


How to Ripen Green Tomatoes

Picked green, tomatoes can be stored in a cool, (55 F, 13 C) moist (90% humidity) location. When you are ready to ripen them, move them to 70 F (21 C).

When researchers tested cherry tomatoes they found the best ripening conditions to be a well-lit spot that does not get too warm. They produced the best color at 70 F (21 C), but they were sweeter when ripened at 79 F (26 C).

You can also wrap the tomatoes in paper and store them in a box. All the paper does is keep them from touching each other. The closed box will help keep ethylene levels higher. Store these cool until they show some reddening and then warm them up for a final ripening period. Only store fruit that does not have diseases, or damage that could lead to rot.

These methods only work once the development process reaches a critical stage. At present, I don’t have a way to help you figure out what that is, but the closer to mature, the better. You will just have to experiment.



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