Growing Walnuts

Climate Requirements

• Walnut is one of the temperate climate fruit varieties so it is very sensitive to high temperature and freezing colds.
• It doesn’t give good results in the high wind areas. Temperature higher than 40 °C in summer, causes sun burns on the green shell and leaves, also the inner gets shrank.
• Walnut is a plant of regions with long and dry summers. Low summer temperatures of those regions located in North or the regions with chilly mountain climate, causes a decline in inner yield. Walnut trees need long seasons in order to ripen their fruits. Walnut spreads throughout the regions 1700 m higher above sea level.
• Walnut trees can resist up to -25 °C in the winter colds. Fresh stools of young walnut trees get harmed at – 9 °C.
• Late spring frosts do the most harm to walnuts in the period when newly emerging buds burst. Closed buds resist up to –1°C, in full blossoming they resist up to –3 °C and little green fruits resist up to –1 °C. Getting harmed by the cold weather depends on the lowest air temperature, falling velocity, and time.
• Chilling requirements for walnut varieties change from 500 to 2000 hours under +7 °C. In order to get products regularly, chilling requirements of walnuts should be fulfilled.
• Varieties with high chilling requirements should be planted in the regions with mild winter climate. Otherwise, varieties that cannot get their chilling requirements fulfilled wake up abnormally late and blossom irregularly. Also the fruit quantity decreases and branches may get drained.
• In cultivation walnut, it is important that annual precipitation is regular and 500 mm at least. Late precipitations of spring increase the bacterial spots on walnuts and walnut anthracnose. Precipitations after the fruits get visible maximize the infection. Late-leafing varieties have bigger chance to get rid of diseases. There are also differences in varieties with regard to being resistant to diseases.
• Rainy and very windy weathers during the blossoming time may affect the pollination and fertilization process negatively.

Soil Requirements

• Walnut has a strong root system that can go down deep up to 2-4 m. Therefore, in the regions with limited soil depth, problems in cultivation may occur. In order not to confront problems in the future, soil depth should be at least 2 m and soil should be permeable.
• Walnut trees are not too selective in terms of soil requirements. However, it grows better in the permeable, rich in nutrient, alluvial, humid, well-drainage, not too hydrophilic soils that have underground water levels not higher than 2.5-3.0 m. Walnut is resistant to lime.
• It has been seen that when planted in the fertile soils or soils increased in productivity by cultural precautions such as watering, walnuts grow faster and fruit productivity gets higher.
• The most important factors that limit the walnut cultivation with regard to site selection, are underground water level and water quality. High humidity and still water block the oxygen uptake of roots, therefore root growth slows down and finally growth of the trees stop. It cannot ripen the annual stools. Spaces between ribs become green and the ribs become brown in color. Edges of stools dry out. If high underground water level doesn’t get lowered by opening the drainage channels, tree dries out completely within few years. In such gardens, fruit trees don’t show any bad indications during the growth however when the length of 5-7 years old fruit trees become 5-6 m, walnuts get out of order in terms of growth and starting from the areas with higher underground water in the garden, trees get dry out.
• Walnut is in the group of moderate fruits in terms of resistance to soil salinity. Soil pH scale should be around 6-7 and there shouldn’t be alkalinity and salinity problem.