Blindness in Roses: Effects of High Intensity Light and Blind Shoot Prediction Techniques1

Abstract

‘Tropicana’ rose plants ( Rosa hybrida L.) were exposed to increasing periods of high intensity light (640 W/m 2 ) beginning immediately after flower removal, in the fall and winter of 1975 and spring and summer of 1976. Flowers were also removed from ‘Forever Yours’ and ‘Cara Mia’ plants in the summer of 1976 and shoot length, stem diameter and bud diameter were evaluated as morphological indicators of blind shoot development. Plants were transferred to a growth chamber (300 W/m 2 ) following the high intensity lighting treatment. Plants grown in the growth chamber without supplemental lighting had the highest percentage of blind shoots. Maximum blindness occurred during the winter months regardless of lighting treatments. Blind shoot production decreased with increased duration of supplemental lighting. Shoot length proved to be an effective indicator of blind shoots as early as 10 days following lateral bud initiation on all cultivars. The value of bud diameter and stem diameter as indicators of blindness was dependent on cultivars.