Seasonal update 2022: GDD, first fall frost and harvest

Thursday, October 6, 2022

At the beginning of this week some parts in the province were hit by the first frost of the season and in some cases the temperatures decreased below zero. It’s important to keep in mind that those areas affected with low temperatures will have change in the canopy, turning color to yellow, red, getting brown in some cases and starting to fall. Also, Jeff Franklin from AAFC Kentville is sharing with us the weather information of growing degree days, which is slowing down as October is starting. Hybrids are still being harvested and getting close to the end, while vinifera varieties are in harvest mode. Just remember, it’s always important to reach out the wineries to know which are the grape ripening requirements and when would be the best time to harvest the grapes.

The first table shows the temperature base 5⁰ C and 10⁰ C from 2019 until 2022 accumulated from March 1 until October 4. At the end of each section, it’s possible to see the average of the last 5 and 10 years respectively.






5 year average

10 year average

Plant development (Base 5ºC)







Insect development (Base 10º)







Figure 1. Degree day accumulations as of October 4, 2022.  All data are taken from the Kentville weather station, based on a start date of March 1, and calculated using the single sine method.

Like last week the accumulation of degree days has slowed down as the season is moving on and the first frosts at the beginning of this week. Compared to the 5- and 10-year average, 2022 maintains a considerable higher accumulation of degrees. It’s possible to see a slightly difference with 2021 and the biggest difference is compared to 2019. Keep track in your vineyard on how the look the current conditions, grape quality conditions and the harvest dates for future management decisions.

In the following column graph, you can see the values from 2005 until 2022 and at the end the average of the last 5 and 10 years respectively.

Figure 2. Degree day accumulations as of October 4, 2022 base 10⁰ C. All data are taken from the Kentville weather station, based on a start date of March 1, and calculated using the single sine method.

Mentioned in the previous table and lasts weeks, in 2022 the accumulation is higher than previous seasons and it is higher than the 5- and 10-year average. Compared to previous seasons of 2021, 2020 and 2018, it’s very similar to the current season and only overpassed by the season 2012. Depending on the varieties and locations, ripening will move differently, for that reason it’s important to keep notes and compare with your previous records.

The first fall frosts happened between Monday and Tuesday this week, reaching different minimum temperatures and durations depending on the location, the topography of the vineyard in each area. With this shift on the temperature, the grapevines, depending on their tolerance to these low temperatures, will show color change in their canopy. In the case of the vines have been already harvested and have been affected by the frost, they will start to slowly shut down and lose their leaves throughout the rest of season. On the other hand, the plants with crop and that have been affected by the frost will start to slow down the sugar accumulation on the grapes and will start to lose their leaves as well. It’s important to keep calm, inform to the winery your current condition and evaluate on how to proceed with them at harvest. Always an open communication and description of your current conditions with the winery will help to take the best decisions.

Figure 3. On the left Frontenac and on the right Chardonnay.

Figure 4. Frontenac canopy with frost damage.

Figure 5. Chardonnay canopy with frost damage.

Harvest is moving on in many varieties, with hybrids in process since a couple of weeks ago and vinifera ones being harvested in different varieties. Already mentioned in this post, active communication with wineries is fundamental to have the grapes harvested depending on the wine goals. It’s important to track grape ripening to help taking harvest decisions and inform to the winery on how the maturity is moving along in your vineyard. Remember, the results will be as good as the sampling performance. The sampled grapes need to be representative of the plot that they are coming from. It’s a good idea to collect a minimum of 100 berries from a specific variety and repeat in the same area(s) to be able to track the ripening process. Alab from Acadia University provides analytical services for grape ripening, please take a look at the lab webpage for more information