Plant Bleaching: what is it and how to do it?

What is the bleaching? For what kind of needs can be a response? How do you put it into practice? In which contexts can you apply it? What coltures can it involve? We gathered some answers in this short article: if we missed someone you need, do not hesitate to contact us! Enjoy the reading.

Who thinks the horticultural activity paralyzes during the winter makes a big mistake. The revival experienced by nature every spring affects the collective imagination more immediately, but also December presents a series of activities that can keep busy those who work in this sector.

First of all, there are winter vegetables that can be sown or transplanted at this time, such as garlic, some varieties of onions, peas and beans. There are others that should be harvested and processed in December, for example, celery, radicchio and other types of chicory.

One of the most important activities that the products we mentioned are in need of is the bleaching. Thanks to it, some products can be much more enjoyable for consumers. We therefore thought to dedicate a short article to this procedure, which maybe you are ready to implement too.

What is the bleaching

The bleaching technique – also known as “etiolation” – takes its name from the fact that it prevents the production of photosynthetic pigments, such as chlorophyll, leading to a whitening of the plant. In addition to this, however, it also has a decisive effect on the taste and consistency of the product, bringing an improvement to its organoleptic properties. 

It is applied to leaf and coast vegetables, whose tissues tend to lignify and take on special colours: celery and horn, fennel, leek, indigo curly or scarlet and various chicory varieties such as radicchio.

Why and when to do it

Bleaching gives us the chance to get the most out of some typical agricultural products of December that would otherwise be mediocre or even inedible. For example, it helps to perfect the radicchio’s colouring and, above all, to make it crispy and softer to taste.

In the case of thistle, which is originally very bitter and fibrous, bleaching is practically necessary; depending on the method employed and the area, it can take from two to six weeks to be done. It is the only challenging phase of its cultivation, since it is a rather robust and easy-to-manage plant.

How it works

The procedure consists of shielding the plant from light with different methodologies; it is completely natural and does not require the use of any product. We emphasize that wrong bleaching can cause the loss of the plant: it is very important to work carefully and with constant control.

Bleaching can take place either in the field – with the help of special agricultural machinery – or after harvesting. One of the simplest methods to do it is through the binding technique, which consists in closing and tying the leaves of each plant, directly in the field, with an elastic or twine.

It is necessary to ensure that the leaves are well dry before the binding: otherwise, moisture may cause rot. The string or elastic should be left for a period between 10 and 20 days, depending on the type of product and temperature: less with high temperatures, more with lower temperatures.

Another way to execute the bleaching of vegetables is the ridging. It consists in covering the plant with the ground, in part (for example up to two thirds of its height) or even in its entirety. If the ground at the base of the plant tends to collapse after rain or wind, it is necessary to recompose it.

In other cases, the plants are placed beneath a cold tunnel shielded by sunlight, for example covered with a black plastic film. The tunnel should be aired at least once every two days; in this way, the plants can be left without light and water for a period of 2 to 3 weeks, until the achievement of the desired bleaching.

Conclusions

We have briefly explained what the bleaching is, how can it be done and in which contexts it is put into practice. Between the lines, we have also mentioned how specific procedures and tools such as binding and ridging can accompany this technique.

Do you want to know more about this topic, for example by discovering which machines are best suited to help you in these operations? Do not hesitate to contact us.