Blueberries - Climate Analysis

How can the climate effect Blueberry growth


How can the growing Environment effect crop growth and health?


Temperature is a crucial environmental factor that influences the development of blueberry plants at various growth stages. Different temperature ranges can impact blueberry growth, photosynthesis, respiration, nutrient uptake, and physiological development.

Warm, sunny days promote blueberry pollinator activity. Blueberries like a warm growing environment, with the most suitable growing temperatures being 15-20 ℃. The plant's cold tolerance and heat resistance are relatively good, and they are able to overwinter.

Blueberries in the growing season can tolerate temperatures as high as 40-50 ℃. When the temperature is higher than 40-50 ℃, blueberries will have reduced growth and vigor due to root system water absorption difficulties.

High temperatures can also disrupt the pollination process, making pollen grains sticky and less likely to disperse, resulting in lower pollination rates and reduced fruit set.

On the other hand, extremely low temperatures can slow down blueberry plant growth and development, inhibit nutrient absorption, and increase the risk of frost damage, which can cause wilting, discoloration, and even plant death.

Low temperatures can also adversely affect fruit development and ripening, resulting in smaller and less flavorful blueberries.


Temperature also affects relative humidity, as warm air can hold more moisture than cooler air. Relative humidity is expressed as a percentage of the maximum amount of water the air can hold. Understanding the effects of temperature on humidity is crucial for optimizing blueberry production in protected environments.

Guidelines for greenhouse blueberries may vary slightly in their recommendations for optimal relative humidity (RH) levels, typically ranging from 50% to 70%.

Effects of high humidity on blueberry plants:

High Humidity can increase disease susceptibility. Increased moisture on the leaves can lead to the development of fungal infections affecting overall plant health. High humidity creates a favorable environment for fungal diseases like powdery mildew and botrytis.

Blueberries require pollination for fruit development. High humidity may hinder the movement of pollinators like bees, potentially reducing fruit set.

Reduced Fruit Quality. Prolonged high humidity during fruit ripening can lead to issues like fruit cracking and reduced quality.

Increased Stress. Blueberry plants may experience stress due to reduced transpiration efficiency in high humidity, potentially affecting growth.

Effects of low humidity on blueberry plants:

Water Stress. Low humidity can lead to increased transpiration, causing water stress in blueberry plants. This is particularly problematic in arid regions or during dry periods.

Reduced Photosynthesis: Extremely low humidity can reduce stomatal opening, limiting carbon dioxide uptake for photosynthesis, and potentially slowing down growth.

Flower and Fruit Desiccation. Insufficient humidity can lead to desiccation of flowers and developing fruits, affecting fruit set and yield.

Drought Susceptibility. Blueberry plants are sensitive to drought stress. Low humidity can contribute to dry soil conditions, impacting overall plant health and productivity.

Vapour Pressure Deficit

Vapor Pressure Deficit (VPD) refers to the difference between the moisture content of the air and the maximum moisture the air can hold at a given temperature. It is a crucial factor that affects water movement within blueberry plants and nutrient uptake by the root system.

Effects of high VPD on Blueberry plants:

Increased Transpiration: High VPD typically results in increased transpiration rates. This means that the plant is losing more water through its leaves, potentially leading to water stress if the plant cannot uptake water from the soil quickly enough.

Stress and Wilting: Blueberry plants may experience stress, wilting, and a decline in overall growth if they are unable to take up water efficiently to compensate for the high transpiration rates.

Reduced Fruit Quality: High VPD can lead to decreased fruit quality, affecting factors such as size and taste.

Effects of high VPD on Blueberry plants:

Reduced Transpiration: Low VPD generally results in reduced transpiration rates. While this may reduce the risk of water stress, it can also limit nutrient uptake by the plant.

Humidity-Related Issues: In environments with consistently low VPD, humidity levels may be high. This can create conditions favorable for the development of fungal diseases, such as powdery mildew.

Slowed Growth: Blueberry plants may experience slowed growth and reduced photosynthesis rates in low VPD conditions, as the rate of water and nutrient uptake may be limited.

Light (Radiation Intensity)

Optimal light conditions for blueberry plants are essential for efficient photosynthesis, which helps them produce sugars vital for growth and development. Adequate light levels also promote the formation of healthy and abundant flowers, crucial for successful pollination and fruit set.

High and low light can each have positive and negative effects on Blueberry plants.

Effects of high Light Conditions on Blueberry Plants:


Increased Photosynthesis: Blueberry plants generally thrive in full sunlight. High light conditions promote efficient photosynthesis, which is essential for the production of carbohydrates and overall plant growth.

Better Fruit Production: Adequate sunlight enhances the development of flowers and fruits. Blueberry plants exposed to sufficient light typically produce more and larger berries.


Heat Stress: In some regions, intense sunlight can lead to high temperatures, causing heat stress. This stress can affect the plant's physiological processes and potentially lead to reduced fruit quality.

Water Management: High light conditions can increase water evaporation from the soil, necessitating careful irrigation to prevent water stress.

Effects of low Light Conditions on Blueberry Plants:


Reduced Heat Stress: In regions with hot climates, some shade or protection from intense sunlight can reduce heat stress on blueberry plants.

Extended Flowering Period: In some cases, moderate shading can extend the flowering period, promoting a more extended harvest season.


Reduced Photosynthesis: Insufficient light can limit the rate of photosynthesis, leading to slower growth and lower yields.

Poor Fruit Development: Blueberries may not reach their full size and sweetness in low light conditions, resulting in smaller and less flavorful berries.

Maintaining optimal light levels within the protected environment is key to gaining the advantages seen in both high and low light conditions, and mitigating the effects of extreme light conditions.

Day/Night Temperature Difference 

Maintaining an appropriate Day/Night Temperature Difference is crucial for optimal blueberry plant growth and health in a protected environment. The Day/Night Temperature Difference refers to the variation between daytime and nighttime temperatures experienced by the plants.

Effects of high Day/Night Temperature Differences on Blueberry plants:

Flower and Fruit Development: High temperature differences can disrupt the normal development of flowers and fruit set. Extreme heat during the day and cooler nights may affect pollination and fertilization processes, leading to poor fruit formation.

Photosynthesis: Excessive heat during the day can increase water loss through transpiration, affecting the plant's ability to photosynthesize efficiently. The stress caused by high temperatures may lead to reduced carbohydrate production, impacting overall plant health.

Stress and Growth Inhibition: Wide temperature variations can induce stress in blueberry plants, inhibiting normal growth and development. Stress may make the plants more susceptible to diseases and pests.

Effects of low Day/Night Temperature Differences on Blueberry plants:

Bud Development and Flowering: Blueberries typically require a certain number of chilling hours at colder temperatures to ensure proper bud development and flowering in the spring. Insufficient chilling hours due to narrow temperature differences may lead to delayed or inadequate flowering.

Fruit Ripening: Blueberries often require a period of colder temperatures to trigger the ripening process. Inadequate chilling can result in delayed or uneven fruit ripening, affecting the quality and yield of the harvest.

Winter Injury: Blueberry plants are susceptible to winter injury if temperatures drop too low, especially during the night. A narrow day/night temperature difference may not provide sufficient insulation, increasing the risk of cold damage to buds and stems.

Maintaining a balance in day/night temperature differences is crucial for the optimal growth and productivity of blueberry plants. Extreme variations, whether too high or too low, can negatively impact various stages of the plant's life cycle, affecting fruit development and overall plant health.

Dew Events 

Dew formation can have negative effects on blueberry growth and health in a protected environment. Dew forms when the plant's surface temperature is cooler than the surrounding air, causing moisture in the air to condense and form water droplets on the leaves and other plant surfaces.

Moisture on the leaves and other plant surfaces can create a favorable environment for the growth of fungal pathogens and other diseases. These pathogens thrive in moist conditions and can cause diseases such as gray mold, anthracnose, and leaf spot. If left untreated, these diseases can significantly reduce blueberry crop yields and quality.


What actions can be taken if we do not have optimal growing conditions? 


To mitigate the effects of extreme temperatures, growers can implement various strategies. For high temperatures, shading techniques can be used to reduce direct sunlight and lower the temperature inside the protected environment. Proper ventilation and airflow are also crucial to dissipate excess heat and maintain optimal temperature levels. This can be achieved through the use of fans or vents.

In the case of low temperatures, growers can use heating systems to maintain a suitable temperature range for blueberry plants. This can include the use of heaters or heating mats to provide supplemental warmth. Additionally, insulating the protected environment with materials such as row covers or thermal blankets can help retain heat and protect the plants from cold temperatures.


To mitigate the effects of both high and low humidity, growers can implement various strategies. 

Ventillation. For high humidity conditions, proper ventilation and airflow are essential to reduce excess moisture in the air and promote air circulation. This can help prevent the growth of fungal pathogens and diseases.

Irrigation. Provide consistent and adequate irrigation to mitigate water stress in low humidity and maintain soil moisture in high humidity.

Fungicide Application. In regions prone to high humidity and fungal diseases, consider preventive fungicide applications.

Pruning. Pruning can help increase airflow around the plants and reduce humidity levels around the plants.

Monitoring. Regularly monitor the plants for signs of stress, disease, or inadequate pollination, and adjust management practices accordingly.

Vapour Pressure Deficit

To optimize blueberry crop growth in a protected environment, it is important to carefully monitor and manage the VPD. This can be done through proper climate control measures, such as adjusting ventilation and humidity levels. Maintaining the right balance of humidity can help ensure that the VPD is within the optimal range for blueberry plants.

Additionally, providing adequate airflow and ventilation can help prevent excessive humidity and reduce the risk of disease development. Proper ventilation can also help regulate the VPD and create a more favorable growing environment for blueberries.

Light (Radiation Intensity)

To ensure optimal blueberry crop growth and health, it is important to provide the right balance of light intensity. This can be achieved by carefully managing the amount of sunlight that reaches the plants. In a protected environment, growers can use shading techniques to reduce the intensity of sunlight during peak hours, protecting the plants from excessive radiation while still allowing sufficient light for photosynthesis.

Day/Night Temperature Difference 

In a protected environment, maintaining an appropriate Day/Night Temperature Difference can be achieved through proper climate control measures. This may involve adjusting the ventilation and cooling systems to regulate the temperature during the day and insulating the structure to prevent excessive heat loss at night.

Regular monitoring and adjustment of the temperature difference based on the specific needs of the blueberry variety being cultivated can help ensure optimal growing conditions and maximize the plants' potential.

Dew Events 

To mitigate the negative effects of dew formation, growers in protected environments can take several actions. One approach is to provide adequate ventilation and airflow within the growing area to reduce humidity levels and prevent moisture from accumulating on plant surfaces. This can be achieved through the use of fans, vents, and other ventilation systems.

Heaters can also be used to maintain a high enough temperature to prevent dew formation. However when using heaters it is important to measure humidity levels to ensure environmental conditions do not increase the risk of fungal pathogens.

Another strategy is to prune the plants appropriately to allow for good air circulation. This can help to reduce the amount of time that the plant surfaces remain wet and minimize the risk of disease development. Additionally, growers can apply preventive measures such as using fungicides or applying organic treatments to protect the plants from fungal diseases.


 How does FarmRoad calculate optimality? 


  1. Every Monday, FarmRoad looks back at the past 7 days of climate data.

  2. FarmRoad then categorises the climate data from each hour of the week  into optimal, sub-optimal or adverse for plant growth and yield based on data science and crop knowledge.

    • Optimal - best for growth and yield

    • suboptimal - not best conditions, but not threatening to plant

    • adverse / extreme - threatening to plant e.g. temperature below 5°C

  3. We do this for each climate factor including:

    1. Estimated VPD

    2. Temperature

    3. Relative Humidity

    4. Light

    5. Day and Night Temperature differences

  4. FarmRoad's Climate Analysis algorithm takes into account your farms location, crop, and season to intelligently analyse only the hours that matter.
    1. For light this means we analyse daylight hours
    2. For Day and Night Temperature difference the hours which are day or night change throughout the year.
  5. FarmRoad then calculates the proportion of time your growing environment was in each specific condition:

    • Optimal ( % and hours)

    • below optimal ( % and hours)

    • above optimal ( % and hours)

    • extreme low ( % and hours)

    • extreme high ( % and hours)

  6. FarmRoad also then calculates how many times your growing environment experienced time in which dew could form - a Dew Event.

    1. FarmRoad does this by analysing when Temperature goes below Dewpoint for a significant period. 

What does 'Optimal' mean?

FarmRoad categorises your climate data into optimal or adverse for plant growth and yield based on data science and crop knowledge.

    Extreme Low Below Optimal Optimal Above Optimal Extreme High
Humidity Day <40 40-50 50-70 70-85 >85
Night <40 40-50 50-70 70-85 >85
Temperature Day <10 10-20 20-27 27-35 >35
Night <10 10-15 15-20 10-25 >25
Radiation Summer >50 50-240 240-360 360-480 >480
Winter <50 50-240 240-360 360-480 >480
Day Night Temperature Difference   <2 2-3 3-5 5-7 >7
VPD   <0.5 0.5-0.7 0.7-1.0 1.0-1.2 >1.2
Dew Events   Dew Events are determined by analysing when Temperature goes below Dewpoint for a significant period.