the nonannual fruiting of fruit and forest trees. Usually all fruit trees yield an annual harvest when they are young, but as they grow older they bear fruit periodically, often every other year. When poorly maintained, young trees may also bear periodically. Trees bearing stones or berries usually yield an annual harvest. In forest trees (such conifers as pine and spruce) and fruit trees, alternate bearing is caused to a large degree by climatic conditions, and it decreases from west to east.
The proper care of fruit orchards provides for the necessary concentration of nutrient substances in the plant cells, especially protein matter, and for an optimal ratio of carbohydrates and nitrogen, which stimulates the setting of flower buds in the harvest year for fruiting in the next year. In this way, annual harvests are ensured. To obtain a good harvest of high-quality fruit every year a tree must have 30 to 60 leaves for each fruit. This is possible if the tree has many annual shoots; thus, shoot formation is an important factor in high yield. Moderate flowering is one of the most important conditions for annual fruiting. Only a moderately flowering tree is capable of producing a large harvest and setting flower buds for the following year’s harvest. Abundantly flowering pome trees (apple and pear) should have their excess flowers or set fruits removed at an early stage of development by growth substances to preserve nutrient matter for the formation of the remaining fruits.
Alternate bearing characterizes only some plant varieties. For example, some varieties of apple (Slavianka, Pepin shafrannyi) yield annually, others (Antonovka obyknovennaia, Anis polosatyi) require special maintenance in order to do so, and still others (Kandil’-Sinap, Grushovka moskovskaia) are marked strictly by alternate bearing. Various agricultural procedures and the stocks to which varieties are grafted also influence the periodicity of fruiting.
REFERENCEPlodovodstvo. 2nd ed. Edited by V. A. Kolesnikov. Moscow, 1966.
V. A. KOLESNIKOV