»APOPLEXY« OF THE APRICOT TREE IN CONNECTION WITH THE HEIGHT AND TYPE OF THE TRUNK

Bulgaria is situated in the southern part of the temperate climatic zone. In general, the country has a moderate continental climate, the western part having climatic conditions similar to those of the Middle-European climatic zone, the north-eastern part being influenced by the East-European climate, while some southern regions of the country are under the influence of the Mediterranean climate. Though small in territory, Bulgaria has many regions with diverse climatic conditions because of the existance of mountains (26 per cent of the territory are mountainous regions with an altitude of over 600 m.), hills (43 per cent of the territory are hilly regions with an altitude of 200 to 600 m.), and plains (31 per cent of the territory is a plain, even country, with an altitude up to 200 m.). The country's territory is transversed and irrigated by several rivers, its nothern boundary being the Danube River, the eastern one being the Black Sea, while its southern boundary runs in close proximity to the Aegean Sea, whose influence is felt in South Bulgaria.

A characteristic aspect of Bulgaria's climatic conditions, and especially of those of South Bulgaria, is the occurrence of frequent warming up of the weather during the winter, while towards its end and at the beginning of spring the country often suffers from late colds, the latter being unfavourable for apricot tree growing.

The period of deep dormancy of the apricot trees in Bulgaria continues up to the end of December. The subsequent warming up of the weather leads to emerging out of the forced dormancy phase and diminishes the cold resistance of the trees, and in case of a prolonged warm weather, might lead to blossoming. Due to the drastic decrease of the cold resistance and to the cold weather which ordinarily follows the warming up, damage to the flower buds and to the trees in general may be inflicted even by moderately low temperatures.

The greater warming up of the weather during the winter months in South Bulgaria explains the higher percentage of perished apricot trees and their more irregular fruit-bearing, compared with those from North Bulgaria, where the climate is more constant and without great spells of warm weather during the winter.

Apricot trees in Bulgaria perish most often in the period between their third and sixth year. Of this range, highest percentage represents 4 year old trees, followed by those 5 years old.