Corriveau, J., Gaudreau, L., Caron, J., Jenni, S. and Gosselin, A. 2012. Testing irrigation, day/night foliar spraying, foliar calcium and growth inhibitor possible as cultural practices to reduce tipburn in lettuce. Can. J. Plant Sci. 92: 889-899. Most of the lettuce produced in Quebec, Canada, is grown in organic soils in the area south of Montreal. Regularly, producers experience tipburn damage to their crop, a physiological disorder associated with Ca deficiency along the margins of young actively growing leaves. Therefore, active research is ongoing to reduce damage associated with this disorder. Two greenhouse trials on Romaine lettuce (Lactuca sativa L. ‘Sunbelt’) were conducted to measure the effect of day and night foliar water spraying, irrigation, foliar application of prohexadione calcium (a growth inhibitor) and foliar application of Ca on lettuce growth and incidence of tipburn. None of the treatments had a significant effect on biomass, dry weight, leaf number or leaf area in lettuce. However, the results show that frequent foliar applications of Ca as low as 90 mg L^-1 Ca² resulted in a significant decreases in the number of leaves and percent leaf area with tipburn, and significant increases in Ca content in young leaves. Foliar water spraying, irrigation and foliar application of prohexadione calcium resulted in no significant differences in tipburn in greenhouse experiments. As greenhouse and field conditions may differ importantly, Ca application should be tested further at the field scale.