The apple orchards studied had discontinuous canopies of LAI from 1.0 to 1.4. These low values for LAI were largely caused by the presence of alleys between the trees, up to one-third of the ground not being covered by tree canopy. Leaf area indices ranged from 0 in the alleys to over 3 in the tree centres. Consequently there was great variation in the angular direction from which different parts of the trees received the greater part of their illumination. Light sensors responding equally to light at all angles above the horizontal were therefore used. Different results were obtained with such sensors and with otherwise identical ones with a cosine law response. Using the 180⚬ equal-response sensors, light intensity in the denser parts of the trees and under tree centres was about 10% of that above the canopy. Within the main fruiting zone of the canopy light intensities were from 30% to 95% of full sunlight. Large and well-coloured fruits were only found under conditions of high light intensity. A more even distribution of the foliage over the orchard would have increased the volume of adequately illuminated canopy.