L'Bleaching it is a manual cultivation practice that consists in preventing the sun's rays from reaching the heart of the plant: in this way the vegetables will be lighter in some parts. Thanks to this technique, various ribbed and cut vegetables such as curly endive, escarole, leek, fennel, celery and thistles become more tender and crunchy.
However, it should be noted that if on the one hand the bleaching gives leaves, stems and ribs richer in water and sweeter, on the other hand it makes them less nutritionally rich. Basically, those who love the bitter taste and leathery vegetables can do without it; in fact, bleaching is not a fundamental process in the cultivation of vegetables, it only serves to improve the organoleptic qualities of the product. For some vegetables, such as thistles, bleaching is almost necessary, because it makes them less fibrous and more tender.
How is bleaching performed?
Endive, escarole and romaine lettuce are tied with a rubber band or a small string about ten days before picking them; when the tufts are well formed and the leaves well dry. Since humidity could lead to the formation of internal rot, it is good to be careful with watering: it will be sufficient to wet the soil and not the leaves.
Celery and thistle are instead wrapped, as if they were huge candies, with sturdy paper. Alternatively, we can use cardboard or packaging bags. In any case, they must be tied tightly in the center with the head protruding from the casing. Again, it is preferable to wait until the weather is dry. For celery, 20 days before harvesting may be enough, while for thistle it is better to bleach one month before.
For leek and fennel (but also for celery) it is enough to make a simple hilling a week before harvesting, bringing the earth back to the base of the plant for about a third of its height and compacting it when it tends to collapse.
Another cultivation technique to make vegetable leaves white and crunchy is tamping: it consists in piling the earth around the stem of the plants as soon as they begin to sprout: in this way the plants will be protected not only from light, but also from frost and from weeds. To facilitate the tamping operation, the stems of the leaves must be held together with cardboard or paper in order to pile the earth all around with a spade.
Fennel and leeks are huddled a week before their harvest. The fruit must be covered by the ground for about one third of its height. After rain or wind, the earth must be recompacted.