Microclimate, referring to the localized climate conditions that differ from the surrounding areas, plays a vital role in shaping the physiology of coffee plants and the quality of the coffee seeds they produce. These localized conditions include variations in temperature, humidity, sunlight, wind patterns, rainfall etc. The coffee plant, Coffea spp., is particularly sensitive to environmental factors. The intricate interplay of temperature, humidity, rain and sunlight creates specific growing environments that can enhance or hinder coffee physiology and quality. Understanding and managing microclimates is essential for coffee farmers aiming to produce high-quality coffee with distinctive flavor profiles. As climate change continues to alter global weather patterns, the study and adaptation of microclimate management strategies for individual varieties will become increasingly important for sustaining coffee production and quality.

At POMA, we strive to develop new agricultural tools and techniques to optimize coffee production – both in terms of profitability and quality. To best do this, we are continuously exploring how different varieties react to all types of microclimates in our climate-controlled greenhouse at the Research Station. To mitigate some of the issues we are facing with climate change, and to optimize growing conditions for specific varieties, we are testing innovative strategies such as induced shading, essential gas-accumulation, canopy-altering pruning strategies, irrigation, and fertigation on farm-level with our partner farmers.

Effects of Temperature

Temperature is a crucial factor altering coffee physiology. Optimal temperatures for coffee growth range from 18°C to 24°C depending on the variety and interplay between other factors. Higher temperatures can accelerate the plant's metabolism, potentially leading to faster growth and earlier ripening. The faster growth will have a positive impact on yields through initiation of new fruiting wood, however, an earlier ripening will lower the seed quality as cell-filling will be impaired substantially. Cell-filling is crucial to obtain a high seed quality, as nutrients and sugars that take space in the cells are precursors for aroma compounds giving coffee its intensity and complexity. Excessively high temperatures, particularly above 30°C, can cause stress, leading to reduced photosynthesis, impaired growth, and lower seed quality. Conversely, lower temperatures can slow down the growth process and delay ripening. This will have negative impacts on yields, as lesser fruiting wood will be created, though, quality will be higher as cell-filling of the seeds will be optimal. If temperatures drop too low, especially below 10°C, it can cause cold damage, leading to plant injury.


Microclimates that provide optimal temperatures for a specific variety contribute to producing high-quality coffee seeds and a good plant vitality. Regions with significant diurnal temperature variations, where days are warm, and nights are cool, can enhance the development of a range of sugars and organic acids in the coffee beans, responsible for synthesizing aroma compounds, improving their quality and complexity. 

As shown in the tables, cooler temperatures extend the ripening period, increasing seed sugar concentration and seed density. This results in a greater intensity and complexity of aroma compounds, particularly encouraging the production of desirable compounds such as terpenes and high-quality long-chained fruity esters. However, this extended ripening can compromise yields in the following year due to reduced shoot growth and less fruiting wood. Conversely, higher temperatures accelerate ripening but lead to the dominance of less desirable aroma compounds, such as nutty esters. Extremely low temperatures can prevent ripening in some varieties, like Caturra, while even chill-tolerant varieties like Gesha suffer from reduced quality and yields due to cold stress. At excessively high temperatures, heat stress becomes prevalent, leading to reduced photosynthesis, impaired growth, and lower seed quality.

We also see that with significant diurnal temperature variations - where days are warm and nights are cool - the development of sugars and density is enhanced in the coffee seeds for some varieties, such as Gesha, while it remains unchanged for a variety like Caturra.

Effects of Humidity

Humidity significantly affects coffee plant health and seed quality. Coffee plants thrive in environments with moderate to high relative humidity (RH), typically between 60% and 80%, for optimal gas exchange conditions. 

When RH is high, the air is more saturated with moisture, reducing the rate of transpiration. Lower transpiration rates help the coffee tree conserve water, which can be beneficial in dry conditions. However, too little transpiration can also reduce the plant's ability to cool itself and may affect nutrient uptake, as these processes are linked to water movement through the plant. Additionally, stomata can remain open for longer periods, facilitating CO2 uptake and maintaining higher photosynthesis rates, which can support growth and potentially improve yields.


In contrast, low RH increases the rate of transpiration because the drier air draws more water out of the leaves. This can potentially lead to water stress if the roots cannot absorb enough water to compensate. Prolonged water stress can lead to wilting, reduced growth, and even leaf drop, negatively impacting the tree's health and productivity. With low humidity, to prevent excessive water loss, coffee trees may close their stomata. While this conserves water, it also limits CO2 intake, which is essential for photosynthesis. Reduced photosynthesis can slow growth and lower overall productivity.

The effects of relative humidity on coffee tree physiology and quality can be seen in the table below.

Effects of Rainfall

Adequate rainfall is essential for the growth and development of the trees and fruits to drive the plant processes and tissue development. Water from rainfall is vital for photosynthesis. Adequate water ensures that the plant can produce the sugars and other compounds needed for growth and fruit development. Rainfall helps dissolve nutrients in the soil, making them available for uptake by the roots.


The onset of rains after a dry period is a primary trigger for flowering in coffee trees. This rehydration breaks the dormancy of flower buds, leading to synchronized flowering, which is important for uniform cherry development and harvesting. 


Microclimates with well-distributed rainfall patterns support consistent flowering and fruit development, leading to uniform ripening and better bean quality. On the other hand, prolonged dry periods can cause stress, leading to incomplete seed development and defects. Controlled irrigation in areas with variable rainfall can mitigate these issues, ensuring optimal moisture levels for the coffee plants.


The effects of rainfall, or in this case simulated rainfall by controlled irrigation, on coffee tree physiology and quality for the variety Caturra can be seen in the table below. 

Effects of Sunlight & Shade

Sunlight is essential for photosynthesis, influencing coffee plant growth and seed development. However, coffee trees require a balance of sunlight and shade. Too much direct sunlight can cause leaf scorching, stress and excessive temperatures, while too little light can hinder photosynthesis, thereby reducing growth and yields.


Microclimates that provide dappled sunlight or partial shade are ideal for coffee cultivation. Shade-grown coffee, often produced under a canopy of trees, benefits from moderated temperatures to increase photosynthetic efficiency and prolong the ripening period. This environment can lead to greater tree vitality and slower, more even ripening of coffee cherries, resulting in seeds with a higher density and thereby a higher quality, intensity and complexity of aroma compounds.


As seen in the tables below, specific varieties react differently to shaded conditions. Varieties originating from shaded conditions, such as Gesha, prefer significant levels of shade to turn productive and to produce a higher quality, while moderate shading is more optimal in terms of productivity and quality for a variety such as Caturra, originating from more sun-exposed settings in Brazil. For each variety, it is an art to find the optimal balance between sun-exposure and shading. 

Effects of CO2 and Oxygen Pressure

Elevated CO2 levels generally enhance the rate of photosynthesis in coffee plants. CO2 is a key component of photosynthesis, where it is converted into sugars and other organic compounds that fuel growth.


Oxygen is essential for cellular respiration, a process that occurs in the mitochondria of plant cells. Through respiration, the plant converts the sugars produced during photosynthesis into energy (ATP) needed for growth and maintenance. Adequate oxygen levels are necessary to sustain this energy production. If oxygen levels are too low (hypoxia), respiration can be impaired, leading to reduced energy availability and potentially stunted growth.


As altitude increases, the overall air pressure decreases. This decrease affects all atmospheric gases. At higher altitudes, the lower atmospheric pressure results in a reduced partial pressure of CO2, which could potentially affect the rate at which plants, including coffee trees, can absorb CO2 for photosynthesis. The effect, however, is more pronounced for oxygen, which is crucial for respiration. At high altitudes, the reduced oxygen levels (due to lower partial pressure) can lead to hypoxic conditions, affecting plant metabolism more significantly than the slight reduction in CO2.


Local factors, such as vegetation density, soil composition, and microclimates, can also influence CO2 levels. For example, in densely vegetated areas, CO2 levels might be slightly higher due to plant respiration, especially during the night.

While CO2 levels do decrease slightly with altitude due to the overall drop in atmospheric pressure, this change is not as significant as the reduction in oxygen levels. For coffee plants growing at high altitudes, the primary physiological challenges are related more to reduced oxygen availability and the effects of cooler temperatures rather than the slight decrease in CO2.