Pruning is carried out in winter, normally once the first frost causes the leaves to fall, thereby exposing the woody canes. Although the precise timing of winter pruning is not generally critical, it should be completed by the time of budbreak in spring, as the pruners can damage emerging shoots as they work. Some early-budding varieties may be pruned very late in an effort to delay budbreak and minimize frost damage. Vines lose water (see bleeding) from pruning wounds just prior to budbreak. In regions with warm winters, such as tropical and subtropical regions, the vines may not become completely dormant, and vines may have to be pruned when they are covered in leaves. See also tropical viticulture.