The objective of this field trial was to investigate causes of the reduced weed population/vegetation in the herbicide strip of fully-grown cv. ‘Elstar’ apple trees. The vegetation in the herbicide strip of cv. ‘Elstar’ with 150 assessments was compared with that under cv. ‘Golden Delicious’, ‘Gala’ and ‘Braeburn’ apple trees on the same rootstock (M 9) at the same location at Klein-Altendorf, University of Bonn, Germany (51º N). To determine the amount of light available to the vegetation in the herbicide strip, light interception of the tree canopy was measured. The 300 ceptometer and the 100 sunfleck measurements with the ‘point quadrat method’ (chessboard) in September after herbicide application in May showed a significant 10% (ceptometer) and 35% (sunfleck) light reduction in the herbicide strip under ‘Elstar’ apple trees relative to ‘Golden Delicious’ in the adjacent tree row.