2019 Volume 65 Issue 2 Pages 75-79
In Tokachi area, the coldest wine-grape-growing region in Japan, canes, cordons and trunks of grapevines of 'Kiyomi' cultivar are buried during fall to prevent freezing damage due to insufficient snow cover during the winter months to protect vines. However, this management is extremely labor intensive as it requires burying and unburying the vines in fall and spring, respectively. The objective of this study was to evaluate seasonal changes in bud cold hardiness of Kiyomi during the dormant season (fall-winter) of 2018/2019, and to identify environmental conditions, i.e. timing and ambient temperature, that could cause freezing damage of unprotected grapevines. During the cold acclimation period in the fall, buds gain cold hardiness and by late November bud cold hardiness exceeded −20oC. However, historical daily minimum temperature data for this region has recorded much lower air temperature during early December than what Kiyomi grapevine buds can tolerate. In fact, on 9th December, 2018, the daily minimum temperature reached −22.1oC. Given the bud cold hardiness of Kiyomi, vines should be protected so that they do not experience temperature below −20oC during mid-winter.
