Under this page, you will find two useful tools to help with your management: GDD and Wild Blueberry Phebology Trackers. 

Wild Blueberry GDD Tracker

Introduction: Growing Degree Days (GDD) is a measure of heat accumulation based on the daily temperature. GDD helps to indicate and assess crop growth stages such as plant emergence, bud burst, flowering and crop maturity during the growing season. We start to calculate GDD depending on the crop and their GDD models. From the start calculation date, each date will generate a GDD value based on its daily temperature. The accumulation of daily GDD will help to determine where your wild blueberry field stage is at, compared to the model we used in Nova Scotia. Here is a factsheet to help you understand GDD in Wild Blueberry Production:

Table 1. Wild Lowbush Blueberry Growing Degree Days Model (White 2012), updated in February 2023

Non-bearing (Sprout) Year

Bearing (Fruit) Year


Cum. Degree-days


Cum. Degree-days

Plant emergence- start

213 GDD

Stems with open flowers- start

390 GDD

Plant emergence- 10%

231 GDD

Stems with open flowers-


412 GDD

Plant emergence- 25%

270 GDD

Stems with open flowers-


440 GDD

Plant emergence- 50%

367 GDD

Stems with open flowers-


480 GDD

Plant emergence- 90%

864 GDD

Stems with open flowers-


600 GDD





Tip Dieback- start

690 GDD



Tip Dieback- 10%

834 GDD



Tip Dieback- 25%

940 GDD



Tip Dieback- 50%

1080 GDD



Tip Dieback- 90%

1475 GDD



*GDD start calculation date: April 1; Base T= 0 °C; GDD calculation method: averaging method (GDD = Tmean – Tbase)

*GDD thresholds in this table were updated on April 24, 2022, from Dr. Scott White’s research data

Table 2. Wild Lowbush Blueberry Fruit Bud F2 Stage GDD, updated in February 2023

Percentage of F2

Growing Degree Days













*The percentage of wild blueberry fruit bud F2 stage and GDDs were based on 1-year field data from 5 sites, developed by Perennia’s Wild Blueberry Specialist (2022). Research in progress. Please use those numbers cautiously. On-going field scouting is encouraged. 

How to Obtain GDDs: we continue to improve our communications and provide clear and easy ways for growers to obtain GDDs as desired. Currently, there are three methods we recommend growers use to track GDDs.

        Method 1: Perennia’s new Farm Data Tools ( 

        Method 2: Check the GDD& Phenology Tracker under Perennia’s Wild Blueberry Blog. Each season, Perennia’s Wild Blueberry Specialist will select some weather stations to monitor seasonal wild blueberry plant development in Nova Scotia. The criteria to pick what stations to report is based on research and extension needs. Please see Figure 1.

        Method 3: Using a GDD calculator sheet. This sheet can be used for any station if you can access the station’s daily temperatures. To download a copy, please go to:


How to Interpret Weather Station GDDs: please compare your current GDD from the interested location (weather station) to the above tables and determine what stage of your fields are at. Please note, variation happens so please make your management decision after you visit your fields. 

Figure 1. Growing Degree Days from Weather Stations located in Nova Scotia Wild Blueberry Fields (running from April 1 to Oct 31)

*Please use the zoom-in and zoom-out functions to change the size of the map and you will be able to see the exact locations of weather stations. 

*Click on the weather station (location) you are interested to know, it will show you the most current accumulation GDD on the date reported. 

*Click on the link under "Current Conditions", and you will be able to see more detailed weather information from the station.

Percentage of Wild Blueberry Fruit Bud F2 Stage Tracker

* Please check back next Spring, 2024. 

Introduction: Wild blueberry buds are at a susceptible stage when 40% or more of flower buds are at the F2 stage. Current recommendations suggest that fungicide application be considered to protect crops when fields reach 40% F2 or above and weather conditions (temperature and wetness period) are conducive to infection.

The below map gives growers ideas of F2 bud stage development in various production areas in NS. Those data were generated based on my observation and reports from growers in those regions. Please check your field and determine your management plant. If you would like to share information with me about the blueberry plant growth stage in your areas, please contact me at 902-890-0472 or email me, at I appreciate your information.