This technique is employed to treat theor of certain vegetables, notably celery, leeks, endive, rhubarb and seakale, so that they remain white and are more appetising. Light is excluded and the plant is therefore unable to make the normal green colouring matter or chlorophyll. The technique varies according to the crop. Celery and leeks are treated by earthing up the soil round the . Seakale is blanched by covering the with or barrels.