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

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 files are at. Please note, that 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 in knowing, 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.


GDD Summary_ April 1- July 15

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 March 2024

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- 10%

412 GDD

Plant emergence- 25%

270 GDD

Stems with open flowers- 25%

440 GDD

Plant emergence- 50%

367 GDD

Stems with open flowers- 50%

480 GDD

Plant emergence- 90%

864 GDD

Stems with open flowers- 90%

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 in March 2024, from Dr. Scott White’s research data


Tables. Other Important Wild Lowbush Blueberry Crop Stages and GDDs, updated in March 2024

Percentage of F2

Growing Degree Days

5% F2

110 GDD

10% F2

121 GDD

20% F2

142 GDD

40% F2

166 GDD

60% F2

191 GDD

80% F2

222 GDD


Percentage of Blooms

Growing Degree Days


 353 GDD

5% Bloom

 365 GDD

10% Bloom

 380 GDD

25% Bloom

 400 GDD

50% Bloom

 431 GDD

70% Bloom

 470 GDD

90% Bloom

 526 GDD


Percentage of ripening fruits

Growing Degree Days

First Blue

1142 GDD

10% ripening

1218 GDD

30% ripening

1354 GDD

50% ripening

1445 GDD

70% ripening

1550 GDD

80% ripening

1610 GDD

90% ripening

1693 GDD

*The results in the above tables were based on multiple years of field data from wild blueberry sites in Nova Scotia, developed by Perennia’s Wild Blueberry Specialist (2024). 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 ( A step-by-step guide on how to use the Farm Data Tools to track GDDs will be available in both factsheet and video formats. Stay tuned and I will let you know when those resources are ready. You can give it a try if you like as it is a fairly simple tool.

Method 2: Check the GDD& Phenology Tracker under Perennia’s Wild Blueberry Blog. Each season, Perennia’s Wild Blueberry will select some weather stations to monitor seasonal wild blueberry plant development in Nova Scotia. The criteria for picking 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:


Percentage of Wild Blueberry Fruit Bud F2 Stage Tracker

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 observations 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.

Figure 2. Percentage of Wild Blueberry Fruit Bud F2 Stage Tracker in NS (running during floral bud development period)