The purpose of pulling leaves and removing laterals (side shoots growing from the main shoot) is to control the amount of foliage on grape vines before bloom.  The leaves and laterals are pulled off by hand and dropped to the ground where they decompose into the soil. By removing the leaves and laterals, bunches become exposed to sunlight and air; this will promote color in red and black varieties. Also, they are now exposed when they bloom and this exposure will allow full coverage of the bloom sprays that will be applied in May.