Blanching

Blanching, or ETIOLATION, is a process of culture resorted to by gardeners, to prevent certain secretions which, in ordinary circumstances, take place in the leaves of plants, and to render them more pleasant and wholesome for food. The action of light is indispensable to the decomposition of carbonic acid by the leaves of plants, and, consequently, to the elaboration of many of the substances from which they derive their peculiar qualities; the exclusion of light, therefore, renders them white or nearly so, and deprives them of much of their natural coarseness and bitterness. In cabbage and some other cultivated plants, the leaves of which form themselves into compact heads, there is a process of natural blanching. Artificial blanching is managed (1) by earthing up the leaves and succulent stems of plants, such as celery, asparagus, &c. For this purpose celery is planted in trenches, and earth is gradually drawn in round the stems as they advance in growth. (2) By tying together the leaves with strings of matting, as is sometimes done with lettuce, endive, &c. (3) By overlaying, which can be done with tiles, slates, pieces of board, or utensils made for the purpose. The most common is the blanching-pot, used to exclude the light from seakale, rhubarb, and some other culinary vegetables, in which the green colour is to be avoided. The common blanching-pot is of earthenware, in a sugar-loaf form, which is used in France for blanching lettuce, and in the Pyrenees for blanching celery, &c. Though so simple and easy, blanching is of great importance in gardening. Without it such a plant as seakale is uneatable if not poisonous; with it the common dandelion has become a wholesome and even medicinal article of salad.