2019/2020 Nova Scotia Wine Grape Bud Hardiness Report no. 7: February 3 – 5

A wine grape bud hardiness report is generated and distributed to the Grape Growers of Nova Scotia (GGANS) membership on a bi-weekly basis throughout the dormant season. The bi-weekly survey is performed on 3 vinifera cultivars (‘Chardonnay’, ‘Riesling’, ‘Pinot Noir’) and 2 hybrid cultivars (‘L’Acadie Blanc’, ‘Marquette’) and involves 10 grower collaborators for a total of 23 varietal blocks in total. Each report uses a table to show the latest low temperature exotherm (LTE) levels for the present and past weeks. The report also includes comments highlighting observations over the last reporting period, a plot showing the change in LTE values throughout the season, the historical 100 year minimum values and the present year’s minimum values. Three times throughout the season (early, middle, late) 11 “extra” varieties (‘Baco Noir’, ‘Chenin Blanc’, ‘Geisenheim’, ‘Leon Millot’, ‘Lucie Kuhlman’, ‘New York Muscat’, ‘Pinot Gris’, ‘Sauvignon Blanc’, ‘Seyval Blanc’, ‘Seyval Blanc’, ‘Vidal Blanc’, ‘Ortega’) from 22 additional varietal blocks are also reported. The LTE50 values of the 5 main varieties in the survey have remained approximately the same since the last survey date. The three vinifera varieties in our survey have not shown any significant changes since the January 6th and 7th survey and have likely reached their deep winter values. Temperatures from the Kentville Research Station show that there have only been 11 days with temperatures below -10 °C so far this winter compared to an average of 21 days below -10 °C for the same time frame over the last 25 years. The relatively milder winter has resulted in a wide margin of safety for our vines in terms of bud freeze damage. It should be noted that in all four years of the survey we have maintained varying degrees of this margin between bud freezing points and observed temperatures, but have still noticed some bud damage in the spring. To help us understand and estimate this damage, we began sampling extra buds in January to estimate bud viability. We will continue this survey over the winter, on a monthly basis, and on a subset of the bud hardiness sites. The results from our first survey date in January are quoted as the %viable primary buds / %viable secondary buds for each of the following varieties: Chardonnay 95% / 81%, L’Acadie Blanc 90% / 96%, Riesling 99% / 92%, and Marquette 100% / 99%. We will report more estimates in the future as the survey continues.