The impact of extreme winter temperatures and spring frosts on fruits

12.07.2026

The impact of low temperatures and spring frosts on apples, plums, and summer grapes

The main risks associated with extreme low winter temperatures and spring frosts

Apples, plums, and summer grapes face many weather hazards that can damage their buds, flowers, and fruits. The main damage is caused by very low temperatures, although the bodies of these fruits can withstand such temperatures. In apples, plums, and summer grapes, there is movement of sap in spring, where the buds begin to swell, and during these developments they lose the ability to withstand cold temperatures, especially if such temperatures occur during the spring period.

Spring frosts are considered a major risk affecting most fruits. The effect of spring frosts on apples, plums, and summer grapes depends on the level of low temperatures, the duration of exposure, as well as the flower development stage. The development stages of apples, plums, and summer grapes are influenced by the following factors:

• Altitude (every 33 meters, blooming is postponed by one day);
• Rootstock (Apples bloom earlier if grafted onto weak vegetative rootstocks);
• Body age (the older the tree's body, the earlier it blooms);
• The harshness of the cuts;
• Location (the same variety blooms earlier in the south and east compared to locations in the northwest);
• Nutrition;
• Protection from diseases and pests;
• The position of the orchard, especially the directions of the orchard rows (north and south);
• The loss depends on the height of the tree's crown. The higher the tree's crown, the greater the loss;
• Food rich in phytohormones and trace elements.
   

However, besides other influencing factors, the three main risks associated with cold temperatures that impact fruit productivity are as follows:

1. Extremely low winter temperatures,
2. Late spring frosts and
3. Early autumn frosts.
   

Critical periods affecting the development of apples, plums, and summer grapes.
The critical period represents the time when buds, flowers, and fruits are very sensitive, and any external factor such as low temperature negatively affects their development and significantly reduces production at harvest time.

a. Extremely low winter temperatures for apples, plums, and summer grapes: The period is considered to be between December 1 and March 19 – when extremely low winter temperatures up to ≤-30 °C may occur.

b. Late spring frosts for apples, plums, and summer grapes: The impact of Spring Frosts (Phase I) from March 20 to April 9 on apples, plums, and summer grapes – this is the bud wilting phase and the most critical phase regarding spring frosts, since most buds, especially the ovaries, are very sensitive to low temperatures.

The impact of spring frosts from April 10 to April 30 (Phase II) on apples, plums, and summer grapes – this is the flowering phase when flowers appear.

A longer flowering period allows for greater opportunities for normal pollination, digestion, and planting of apples, plums, and grapes for summer. For each flowering day that occurs earlier than the average flowering date, the chances of frost increase. From the above factors, it can be seen that flowering occurs at different times in different places for the same variety of apples, plums, and summer grapes. In the regions of Kosovo, flowering begins earlier in the regions with lower altitude and later in the higher altitude regions such as Prizren (April 20), Ferizaj (April 28), and Dragash (May 12). Once the flowering period begins, a severe frost can cause serious damage to flowers depending on the duration of the frost.

The impact of spring frosts from May 1 to May 15 – Spring frosts (Phase III) on apples, plums, and grapes for summer; this is the period of fruit formation. The newly formed fruits of fruit trees are very sensitive to late spring frosts - Phase III.

How can farmers mitigate these risks?

There are two methods that farmers can use to protect themselves from possible losses or to mitigate these losses. Agricultural insurance for apples, plums, and summer grapes,

• Agro-technical measures as direct actions.
  

The agricultural insurance model based on the weather index model for apples, plums, and summer grapes has been proposed as the most suitable and practical model to start agricultural insurance in Kosovo.

The advantages of the index model compared to traditional insurance are listed below:

• Index insurance also enables coverage for small and individual farmers;
• No specialization in agriculture is required for insurance company personnel;
• No expertise is required to sell the policies;
• In case of losses, no assessment of the losses incurred is required;
• Index insurance is transparent as it allows policyholders to have direct access to the information on which payments will be calculated;
• Low operating and transaction costs.

Traditional insurance is not suitable for application in Kosovo at the moment, as it requires deep expertise and knowledge of insurance, risk assessment, and loss evaluation.

Agro-technical measures to prevent damage from extremely low winter temperatures and late spring frosts
The indirect measures are:

• Choosing a good geographical location to establish an orchard,
  
• Choosing species and varieties that bloom later,
   
• Covering the trunks of fruit trees with snow,
   
• Watering fruit trees for about ten days before flowering.

It is known that fruit trees during their flowering period are more affected by frosts at low altitudes and in southern and southwestern positions, so it is recommended to avoid these locations. Some early apple varieties bloom earlier and are severely damaged by late spring frosts, so they should not be planted in such areas. Use only late-flowering varieties that avoid late spring frosts.

By placing snow around the trees, the risk of late spring frosts can be largely avoided during the flowering period. Its effect is based on cooling the root system from melted snow. To prevent the snow from melting quickly, it should be laid as a strip and then covered with straw.
Irrigation, when conditions allow, if done about ten days before flowering, achieves an effect similar to snowfall, because water cools the roots of fruit trees and they begin to absorb moisture and inorganic matter much later, resulting in a later flowering of fruit trees by several days. Indirect measures do not always provide complete protection but only reduce the risk.

The direct measures are:
Smoke or fogging from an orchard is the safest measure to combat late spring frosts. This is the cheapest method, and success is achieved if cold temperatures are not too harsh, because this reduces the temperature to 1.5°C. Smoke is created by igniting materials that produce very dense smoke.

Orchard heating - Air heating in orchards is a safer protective measure, but it is quite expensive and applied only to fruit trees with high intensity. Heating is done with special furnaces, where charcoal is used instead of wood.

Artificial rain - Artificial rain irrigation of fruit trees during the flowering period can prevent the occurrence of late spring frosts. In this case, the temperature can rise from -5° C to -1° C. Spraying stops when the ice on the branches begins to melt.

General conclusion: - Apple, plum, and wine grape growers, in order to avoid losses due to climatic conditions (late spring frosts and deep winter frosts), should use both of the above-mentioned measures. These two measures are of particular importance and complement each other: ensuring the agricultural index and implementing agro-technical measures. The implementation of these two measures helps farmers reduce losses to a level acceptable to the farmer.