Recovery of Sultana vines after spring damage

Abstract

Sultana vines damaged in spring by frost or hail have been studied. The destruction by frost of half the shoots present when bud burst was nearly complete did not result in the bursting of more than a t the most one-quarter of the primary buds which would normally have remained dormant. Primary buds bursting after the frost produced a much lower proportion of fruitful shoots than those bursting before. There was reduction in yield due not only to the smaller number of bunches but also to a decreased average bunch weight. Canes formed for the next season on vines frosted in early spring had more fruitful buds in the distal region and a higher overall fruitfulness. Canes formed on vines damaged by frost or hail much later in the season had fewer fruitful buds in the proximal region and a lower overall fruitfulness. Repruning of sultanas immediately after frost or hail to improve the yield in the same or the following season is not justified, but at the following winter pruning the canes should be left with more buds than usual.