Seasonal and regional variation in budbreak and flowering of kiwifruit vines in New Zealand

Abstract

Measurements of the timing and amount of budbreak and flowering in ‘Hayward’ kiwifruit were made over 4 years in six regions of New Zealand. There was a large variation in the vine attributes measured. The number of flowers produced/winter bud varied 5‐fold between the worst site‐year combination and the best. The time of 50% budbreak varied by 32 days and the time of 50% flowering by 25 days. The proportion of flowers on the distal (tip) two buds ranged in a single year from a low of 10% at one site to > 65% at another on canes which had an average of 21 buds. The number of flowers/winter bud is considered to be made up of four components: the proportion of budbreak, the proportion of floral buds, the number of inflorescences/floral bud, and the number of flowers/ inflorescence. The proportion of budbreak and the proportion of floral buds were found to be most important in determining the number of flowers produced/winter bud, and both of these components were significantly higher at the cooler, southern, sites. The vines measured in this survey were all chosen from a single block in a single orchard within each region, so between‐vine variation was minimised. Despite this, total between‐vine variation accounted for nearly 40% of the observed variance in the proportion of budbreak and about a quarter of the observed variance in the number of flowers/ winter bud and the proportion of floral buds. Differences between regions were significant for all vine attributes measured except the number of inflorescences/floral bud, with cooler sites generally breaking bud earlier and producing more flowers. When averaged over all 4 years, the number of flowers/winter bud was over twice as high at the coolest site than at the warmest, and budbreak occurred more than 3 weeks earlier. The proportion of flowers on the tip two buds varied from an average of < 17% at one site to > 50% at the warmest site. Year‐to‐year differences were generally not significant when averaged over all regions, except that flowering tended to be early or late at all sites in the same years. Year‐to‐year variation was however very important within each region. Over 50% of the variance in the number of inflorescences/ floral bud was the result of year‐to‐year variation, and over a third of the variance of the number of flowers/winter bud. At the warmest site, both the number of flowers/winter bud and the proportion of flowers borne by the tip two buds varied more than 2‐fold in consecutive years. It is this between‐season variation that is of major significance in orchard management. It is also important for the industry at large because of the need to organise transport, storage, and marketing on a region‐by‐region basis.

Keywords:

• kiwifruit
• Actinidia deliciosa
• phenology
• bud development
• flowering times