If green tomatoes fall off or have little chance of ripening due to cool autumn weather, they may ripen later. Various options are available, which are explained below.
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Post-ripening is important
Harvesting green tomatoes ( Solanum lycopersicum ) always includes post-ripening, because unripe specimens entail health risks. Caution is required, especially with the ingredient “solanine”. This is a bitter substance that makes green tomatoes poisonous from a content of around 25 grams. Consumption is therefore strongly discouraged in order to avoid the following body reactions as typical signs of solanine poisoning:
- stomach pain
- nausea and vomiting
- diarrhea
- Stomach cramps
- From 400 grams of solanine the most severe symptoms of poisoning and possible death
Suitable tomatoes
Only specimens that meet certain conditions are suitable for ripening. The focus is on harvesting healthy tomatoes, as the red fruits are also called in Austria. The following conditions decide whether a green tomato is suitable:
- Is free of cracks and/or mold
- Has already ripened (yellow, sticky flesh indicates insufficient ripeness)
- Has a firm consistency all around
- Has no “glassy” spots (usually caused by low temperatures/frost )
Optimum temperature
The first and most important step towards promising post-ripening relates to the temperature. This plays a key role in how quickly and reliably post-ripening takes place. In this regard, please note:
- Higher temperatures accelerate post-ripening (but fruits have a shorter shelf life)
- At lower temperatures, post-ripening sometimes lasts for weeks
- Should be brought into a warm place before the onset of frost at the latest
- Ripening temperature: between 16 degrees Celsius and 25 degrees Celsius
- Ideal temperature: between 18 degrees Celsius and 20 degrees Celsius
light and humidity
Regardless of which method is chosen for post-ripening, the necessary lighting conditions are always the same. While the fruits on the plants need a lot of light for growth/development, the Solanum lycopersicum ripens best outside the plant in the dark. There is one exception: the fruits only have small green spots. In addition, light can be helpful when fruit is encouraged to ripen on the plant. How these two methods work is described in detail later in the guide.
After harvesting unripe candy apples, the after-ripening depends on a certain level of humidity. If it is too low, the fruits will dry up quickly. If the humidity is too high, rot is encouraged, which attracts fruit flies. The optimum humidity is 80 percent.
Harvest right
If you want to use green fruits from the bush for later ripening, you should take care to cut them off when harvesting. Peeling or tearing can cause cracks that make them unsuitable for post-ripening. For some post-ripening methods, part of the stalk should remain attached to the tomato because it enhances the aroma.
methods for ripening
There are various methods to choose from with which the Solanum lycopersicum can ripen:
bag ripening
If only a few green specimens have to ripen, the bag method is ideal. How it works and what to look out for:
- use clear plastic bag
- place three to four fruits without stems per bag
- Close the bag well
- Poke air holes in the bag
- Location as described above: warm, dark and humid
- Duration of post-ripening: between two and five days
Paper-Method
The paper method works in a similar way to the post-ripening in bags. Things to watch out for:
- Newspaper is ideal (tolerates humidity better)
- Alternative: paper bag (must be closed afterwards)
- Harvest fruits with stems
- Wash and dry the fruit
- wrap a maximum of three to four fruits together (can also be wrapped individually)
- Location: warm, bright and humid as previously described
- Check paper continuously for moisture and replace with dry paper if necessary
- Duration of post-ripening: between two and five days
cardboard method
The cardboard method offers the solution for larger harvests of unripe, green paradise apples. How to do it:
- use a sufficiently large cardboard box
- Lay out two layers of newspaper on the floor
- Spread fruit with stalks on newspaper
- put a layer of newspaper on top
- Distribute fruit in the second layer again
- a maximum of three tomato layers possible
- cover the last layer with a layer of newspaper
- Don’t move or touch fruit anymore
- Location as previously described: dark and humid, but ideally cooler than too warm
- Duration of post-ripening: between three and seven days
Post-ripening in mason jars
Mason jars are a good idea for smaller harvests, and they also take up little space. That’s how it’s done:
- Put the paradise apples in glasses up to a few centimeters below the rim (should lie loosely to avoid bruises and rot)
- close well with lid
- regular checking for mold and rot recommended
- Location as previously described: warm and dark (humidity not important as it is (almost) airtight)
- Post-ripening period: around 14 days
post-ripening on plants
A Solanum lycopersicum can also be encouraged to ripen directly on the plant. There are two different ways to do this that work without any problems:
garden bed
Letting tomatoes ripen on the plant in the garden bed is recommended if suboptimal weather conditions are imminent in autumn and tomato ripening on the plant should be accelerated and promoted in the last suitable days. Here, certain details must be observed and proceed as follows:
- twist the plant
- Avoid ground contact of the tomatoes by covering the ground with foil or a wooden plate (otherwise there is a risk of rotting)
- Minimum temperature twelve degrees Celsius – otherwise protect the plant with fleece or similar insulation
- Maturity depending on the weather: about a week
- End the project early if frosty temperatures are imminent (then cut off fruit for later ripening)
Spatial maturity of the whole plant
If the weather is no longer suitable for post-ripening outdoors, moving to a warm room offers an alternative. The laundry room in the basement is ideal, as there is usually a sufficiently high level of humidity and dark lighting conditions. The procedure is simple:
- Plant the plant and its roots out of a pot or garden bed
- remove all leaves (to prevent wilting)
- Wrap roots with floral wire or ribbon
- Hang the plant upside down from the ceiling or wall with the roots up
- Post-ripening period: three to five days
frequently asked Questions
A window sill and a bright location associated with it should only be used for post-ripening if the fruit has few green spots. In that case, they can be placed in a bowl and placed on the windowsill. It is important that high humidity is also ensured here.
Tomatoes contain ethylene during the ripening process, which acts as a ripening gas and escapes. Covering or wrapping in newspaper or sealing in a paper bag prevents the gas from evaporating. It collects around the fruit and in this way promotes post-ripening.
