Water stress has been used for more than a century in Mediterranean countries to stimulate flowering in lemons. It is important to determine the optimum level of stress at which irrigation should be started after the dry period. Too little stress can promote an inadequate flowering response. Too severe a stress can cause excessive leaf and fruit drop. Moderate water stress is recommended to induce sufficient flowering without excessive fruit drop.
Water stress can also influence cold hardiness.
Mild water stress has been shown to temporarily increase cold hardiness in greenhouse tests, but excessive water stress can weaken the trees and reduce cold hardiness. The old idea that fall irrigation should only be applied when trees are severely wilted appears to be ill-advised. Koo found that after freezes, non-irrigated trees showed more leaf and fruit loss than trees irrigated one to five weeks before freezes. He suggested that temporary leaf wilt at midday could be used as a guide for fall irrigation. With variable fall and winter rainfall, it is difficult to maintain cold hardiness, particularly if the winter daytime temperatures are above normal.