REGIONAL VARIATIONS IN THE RESPONSE OF KIWIFRUIT VINES TO TIME OF CANE TIPPING

Fruiting canes on kiwifruit vines (Actinidia deliciosa (A. Chev.) C. F . Liang et A. R. Ferguson 'Hayward') were pruned to length either at t he usual time during winter, or much later, during spring. Pruning of replacement canes during spring is known as late tipping. Previous stu dies in Te Puke, the major kiwifruit-growing region of New Zealand, ha ve shown that late tipping can increase budburst, and therefore the yi eld, of kiwifruit vines by between 22 and 39%. In the current work, tr ials were carried out in three kiwifruit-growing regions of New Zealan d to determine the range of regional responses to late tipping. When d ata from this trial were combined with previously published data we fo und that changes in the number of flowers per winter bud (FWB) in resp onse to late tipping were inversely related to the proportion of budbu rst (BB) on the canes tipped at the normal time during winter: increas e in FWB(%) = 125-251 x (BE) r(2)=0.73. Therefore, late tipping will n ot increase flower production on vines which are already destined to h ave a high budburst. This situation is likely to occur regularly in cl imates as cool as southern New Zealand, or northern Italy, but less fr equently in the milder climate of Te Puke, New Zealand.