Environmental factors that promote bolting in long-day onions (cv Valencian
a de Grano) were examined. Plants were grown at various densities and light
levels and it was found that the upper temperature limit for flower induct
ion was approximately 17 degrees C and that low irradiance impairs flower p
roduction. To control of bolting whilst maintaining yield requires high lev
els of soil N availability during growth and a leaf area index less than 3.
5.