2018/2019 Nova Scotia Wine Grape Bud Hardiness Report no. 13: April 15 – 19

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.

Large shifts are underway in the bud acclimation values for all of the varieties in our survey. ‘L’Acadie’ buds have experienced the greatest change with a 7 °C drop in acclimation values over the last 2 weeks while ‘Riesling’ had the smallest change at 3.9 °C over the same period. Our last survey date also included some extra varieties that we have been watching over to winter. Table 1 shows that these varieties have also deacclimated significantly since they were last surveyed 2 months ago. In spite of the changes, there remains a significant margin of safety between observed temperatures and the estimated bud hardiness. The lowest observed temperature in Kentville over the last 2 weeks was -4.2 °C on April 9th while the LTE10 values were estimated to be in the -11 °C to -19 °C range. On April 29th and 30th we will be taking our last bud samples from commercial vineyards for this year. We would like to thank all of those who have delayed pruning to give us the source of buds that we need to produce the bud-hardiness estimates. Certainly none of this would have been possible without the collaboration and cooperation of the Nova Scotia Grape Growers.