Each agricultural season brings with it opportunities and challenges, but in high-value fruit crops, few phenomena command as much respect as frost. While cold weather is an inherent part of the temperate and Mediterranean climates where our main productions flourish, its impact can be dramatic when it coincides with sensitive phenological periods.
Frosts affect plant tissues in very different ways depending on the species, the plant's stage of development, the duration and type of frost, and multiple physiological and environmental factors that determine its severity.
When we talk about frosts, we don't just mean the thermometer dropping below zero. The real damage begins to develop inside the plant cells. As the temperature drops, intracellular water starts to migrate to the extracellular space where ice forms. This process of extracellular freezing progressively dehydrates the cells. As long as the process is moderate, the plant can resist; however, if cooling is rapid or temperatures reach extreme levels, cell membranes break and the damage is irreversible.
The phenomenon becomes even more complex when considering the different types of frosts. Radiative frosts, typical of clear and windless nights, cause intense thermal drops in the lower layers of air. On the other hand, advective frosts, associated with the influx of cold air masses from polar latitudes, cover large areas and are difficult to manage due to their intensity and duration.
Beyond the physical and physiological processes, what really matters in Chile is understanding how this phenomenon affects, practically speaking, the crops that sustain our fruit industry. Let's take a detailed look at how different species face this climatic challenge.
The Challenge of Cold in Cherry Trees
The cherry tree, a leader in Chilean fruit growing, shows marked sensitivity to spring frosts. During the winter dormancy, its buds can tolerate drops even as low as -10°C, but this resistance quickly fades as its reproductive cycle begins. When flowers start to open, temperatures as low as -1°C can affect the ovule and pistil, compromising pollination and set. Often, the effects of a frost do not manifest immediately but weeks later, when the lack of fruit set reveals the hidden damage. In newly set fruit stages, temperatures between -1.5°C and -2°C are enough to cause the early drop of affected fruit.
Kiwis and Their Extreme Vulnerability
If cherry trees are sensitive, kiwis take this vulnerability to an even higher level. Being a subtropical species, during bud break and early vegetative development, kiwi shoots cannot withstand temperatures below -0.5°C. A mild spring frost can completely wipe out the season's production. But the risk does not end there: in particularly cold winters, the wood and productive buds can also suffer severe damage, especially in young plantations prior to lignification.
Blueberries: Resilience During Dormancy, Fragility During Blooming
The blueberry shows an interesting duality in response to frosts. During winter, floral buds can withstand extreme temperatures. However, that resistance vanishes in spring. The open flowers and newly set fruits become vulnerable to mild negative temperatures, ranging from -1°C to -1.5°C. Damage not only reduces the harvest volume but also affects the uniformity, size, and commercial quality of the fruit.
The Vine: Fragile Buds at Winter's End
Both table grapes and wine grapes share a similar pattern in response to cold. During their deep dormancy in winter, vines can tolerate drops to -10°C without major consequences. However, danger arises at the start of bud break. The primary buds, essential for production, are extremely sensitive. Temperatures of just -0.5°C can completely eliminate them, forcing the plant to produce secondary buds, which have lower productive potential and affect oenological quality in the case of wine grapes.
Citrus: The Danger of Winter Frosts
In citrus, sensitivity varies by species and stage of development. Flowers, shoots, and developing fruits are extremely vulnerable to sub-zero temperatures. Fruit damage—which remains on the tree throughout the winter—manifests as internal necrosis, loss of firmness, and browning of the pulp. Lemon trees top the sensitivity list, followed by mandarins and finally oranges. The complexity is that sublethal damage can affect budding and next season's productivity, even when symptoms are not immediately evident.
Avocados: The Most Defenseless Fruit Against Cold
Among all analyzed species, the avocado is undoubtedly the most sensitive. Aside from the fact that the fruit remains exposed throughout the winter, its vegetative tissues can suffer damage from 0°C, and temperatures of -2°C are enough to destroy branches, inflorescences, and, in extreme cases, cause the total death of young trees. During flowering, damage to the inflorescences severely compromises set and the season's productive potential. This high susceptibility explains the complexity of managing avocados in areas at risk of winter or spring frosts.
The Most Efficient Defense: Low Precipitation Sprinkling
When the risk of frosts is recurrent, active protection of crops is crucial. Among the various available technologies, water sprinkling stands out for its agronomic and energy efficiency. By applying water to plant tissues during frost, the heat of fusion released during the freezing process helps maintain tissue temperature near 0°C, preventing the cell interior from reaching lethal levels, the so-called "Igloo Effect".
Nowadays, low precipitation sprinkling systems achieve this protection with controlled water usage, reducing risks of soil saturation, excessive ice formation, and compaction. Proper calibration of these systems—typically in the 0.5 to 1.5 mm/hour application range—ensures that the applied water quantity is necessary to maintain thermal balance, maximizing efficiency.
Additionally, this type of system allows for more prolonged operation during extensive frost events, optimizing available water resources and ensuring even coverage over sensitive tissues. Its effectiveness has been widely validated in stone fruit crops, cherries, blueberries, kiwis, vines, and citrus.
An Increasingly Challenging Climatic Phenomenon
In recent years, climate variability has been accentuating both the frequency and intensity of frost events. Climate change not only alters average temperatures but has created a more unpredictable scenario: later frosts, intense cold waves outside usual periods, and risk windows extending into advanced phenological development stages.
This greater climate instability forces producers to adapt and anticipate. Frost protection decisions are no longer a one-time option, but an integral component within the agronomic management of orchards. Implementing active protection systems—such as low precipitation sprinkling—gains increasing relevance as a concrete, effective, and sustainable tool to face this growing challenge.
At Tierraverde, we support producers precisely on this path of adaptation, combining deep physiological knowledge, precision climate monitoring, and specialized technical advice to turn climate risk into informed decisions. Because in the face of the new climate scenario, anticipation is today the best safeguard for productivity.
