How to Protect Hazelnut Orchards from Frost Damage

What Is Agricultural Frost?

Agricultural frost is a meteorological event that occurs when air temperature drops below the level plants can tolerate, causing damage to plant tissues. Hazelnut is the most important crop of Turkey’s Black Sea region, and late spring frosts in particular can cause severe yield losses in orchards during the flowering period.

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Cold Hardiness of Hazelnut

The cold hardiness of hazelnut plants varies greatly depending on their phenological stage:

Full dormancy: Can withstand temperatures down to −25°C
Male flowers (catkins): Killed completely at −8°C
Female flowers: Killed completely at −16°C
Shoot and fruit development: Damage begins below 0°C

Signs of Frost Damage

Frost damage manifests in different ways across the various organs of the hazelnut plant.

Flowers

Male flowers (catkins) turn black and dry out; pollen release ceases
Stigmas of female flowers turn brown and fail to pollinate
Frost during the flowering period can wipe out the entire year’s yield

Shoots and Buds

New shoots wilt from water loss and die back from the tips
Buds may burst from freezing or die before opening
Browning is observed beneath the bark tissue

Nuts and Husks

Small fruits drop or fail to develop fully
Spotting and discoloration appear on the husks
Hollow and shriveled kernels develop inside

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Critical Period: February–April

The most dangerous frost period for hazelnuts in the Black Sea region is between late February and April. During this time, flowering has begun but fruit set has not yet occurred. A single night of frost can destroy the entire harvest.

Active Protection Methods

Active methods are intervention techniques applied when frost threat is imminent or while frost is occurring.

1. Smoke Method

Smoke-producing materials (stalks, straw, dry grass, wet wood) are burned at various points throughout the orchard to prevent the cooling of the air layer near the ground. The smoke acts as a blanket that slows heat loss.

Application:

Set up one fire point for every 500–1,000 m² of orchard area
Start burning when the temperature drops to +2°C on a night when frost is expected
Maintain the smoke until sunrise and temperatures rise
Effectiveness decreases on windy nights

2. Sprinkler Irrigation

The latent heat released when water freezes (80 cal/g) keeps the plant surface at around 0°C. This is one of the most effective active protection methods.

Application:

Sprinklers must be turned on before frost begins
They must run without interruption until the frost ends and all ice melts
Applying 2.5–3 mm of water per hour is sufficient
Shutting off too early can increase damage through evaporative cooling

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Sprinkler Warning

Never shut off sprinkler irrigation before the frost has completely passed. Turning it off early causes evaporation from the ice surface, which drops temperatures even further and worsens the damage.

3. Pre-Irrigation (Pre-Frost Watering)

This involves watering the orchard 1–2 days before frost is expected. Wet soil stores significantly more heat than dry soil and slowly releases this heat at night, keeping the soil surface temperature 1–3°C higher.

4. Physical Covering

Covering trees with mats, cloth, or agricultural frost blankets prevents radiative heat loss. This method is particularly effective for young seedlings and compact orchards.

Points to note:

The cover should not touch the plant directly; use a support frame
Remove covers during daytime to allow ventilation

5. Air Circulation (Wind Machines)

Large wind machines (frost fans) mounted on tall poles direct warmer air from higher layers down toward the ground. This method is effective against radiation frost, and each fan can protect an area of approximately 4–5 hectares.

6. Direct Heating

Heaters, stoves, or fuel containers placed throughout the orchard directly warm the air. This method requires 100–150 heaters per hectare; it is costly but effective.

Cultural (Passive) Measures

Cultural measures are planning and management practices that reduce frost damage risk over the long term.

Selecting Frost-Resistant Varieties

Variety selection is the most fundamental precaution against frost damage. Late-flowering varieties are less affected by late spring frosts.

Variety	Flowering Time	Frost Resistance	Notes
Fosa	Late	High	One of the most frost-resistant varieties
Cakildak	Late	High	Stands out for its late flowering
Tombul	Medium	Medium	The most common variety in the Black Sea region
Palaz	Medium-early	Medium-low	Carries risk due to early flowering

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Variety Diversification

By growing multiple varieties in your orchard, you can spread out the flowering period. This reduces the risk of a single frost event destroying the entire harvest. Plant late-flowering varieties like Fosa and Cakildak alongside other varieties.

Fertilizer Management

Avoid excessive nitrogen fertilization: High nitrogen causes the plant to produce late shoots and increases water content in tissues, raising frost susceptibility
Apply potassium fertilizer: Potassium increases osmotic pressure in cells, lowering the freezing point and improving the plant’s cold tolerance
For a balanced fertilization program, see our fertilization program guide

Creating Windbreaks

Dense-branched trees or hedging plants planted along orchard edges can block cold wind currents and keep the orchard temperature 2–3°C higher. The windbreak should be positioned perpendicular to the prevailing wind direction.

Orchard Location and Site Selection

Avoid low-lying areas: Cold air is heavier and accumulates in depressions (creating frost pockets)
Choose sloped terrain: Cold air accumulation is prevented on slopes with good air drainage
South-facing slopes: Receive more sunlight and warm the soil more effectively

Frost Forecasting and Early Warning

Proper timing is critical for effective frost protection. Pay attention to the following factors when forecasting frost:

Monitor weather warnings: Follow frost alert bulletins from provincial and district agricultural directorates
Install a thermometer in your orchard: Record overnight temperatures with a minimum-maximum thermometer
Weather indicators: Clear skies at night, low humidity, calm winds, and sudden pressure changes are harbingers of frost
Digital sensors: Sensors that continuously measure soil and air temperature enable real-time monitoring

Agricultural Insurance (TARSIM)

Despite all precautions, frost damage can still occur. Through TARSIM (Agricultural Insurance Pool), you can insure your hazelnut orchard against frost, hail, and other natural disasters.

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TARSIM Frost Insurance

Government premium subsidies reduce insurance costs
Frost damage assessments are conducted by TARSIM experts
Claims must be filed within 7 days of the damage occurring
For detailed information: tarsim.org.tr

Conclusion

Agricultural frost is a significant natural hazard that threatens hazelnut production in the Black Sea region. However, with proper planning and timely intervention, damage can be minimized.

In summary:

Hazelnuts can withstand −25°C during full dormancy, but are highly susceptible to frost damage during the flowering period
Sprinkler irrigation and the smoke method are the most common active protection techniques
Late-flowering varieties such as Fosa and Cakildak provide natural protection against spring frosts
Avoid excessive nitrogen fertilization and increase the plant’s cold tolerance through potassium fertilization
Monitor weather warnings and install a thermometer in your orchard
Secure potential losses with TARSIM insurance

For all aspects of hazelnut care, check our hazelnut guide. For winter care details, see our January and February care calendars.

📚 Samsun Provincial Directorate of Agriculture and Forestry 📚 Hazelnut Research Institute 📚 Ordu Provincial Directorate of Agriculture and Forestry