From winter dormancy to the onset of bud swelling (Dec. – Feb.)
During the winter months, apricot trees – as all deciduous trees – are dormant. During this time, the trees have no nutritional requirements, while the flower buds accumulate the hours of cold required and they become fully grown. In February, before bud flushing, there is significant growth and activity in the root system, which culminates in April and is accompanied by the absorption of significant amounts of water and nutrients.
A good supply with the required nutrients since early winter is key for the trees to be able to flower and have a fast vegetative and fruit growth.
- ● Nitrogen (Ν) contributes to the tree breaking dormancy and stimulates early sprouting and flowering, thus leading to increased yields.
- ● Phosphorus (Ρ) boosts the growth and activity of the roots, increasing the absorption of nutrients which are required for flowering, fruit setting, and fruit growth.
- ● Potassium (Κ) regulates the water balance of the tree and takes part in the migration of the stored substances to the buds.
When it comes to trace elements, Boron (Β) and Zinc (Ζn) contribute to bud flushing, flower formation, and increases flowering and fruit setting.
From bud swelling to full flowering (Feb. – Mar.)
In February, as the root system becomes activated and water and nutrients are absorbed, the substances which had been stored in the roots, the trunk, and the branches during the previous growing season are mobilized and migrate to the buds, in order to cover the increased requirements of flowering and fruit setting.
At first the flower buds are enlarged, and in early May they open. Then the new leaves emerge and the elongation of the shoots begins, with flowering concluding in mid-March, with the onset of the formation of the fruits.
Nutrient adequacy at this stage has a determining effect on the development of fruit setting and the annual production.
- ● Nitrogen (Ν) supplies the buds and flowers with proteins, and boosts leaf growth as well as fertilization and fruit setting.
- ● Phosphorus (Ρ) provides the tree with the necessary energy for flowering and the structural elements for fruit setting and fruit growth.
- ● Potassium (Κ) starts accumulating in the forming fruits and participates in their growth process.
When it comes to trace elements, Boron (Β) increases pollen germination and increases fruit setting, while Zinc (Ζn) and Iron (Fe) are necessary in order to cover the needs of sprouting.
From fruit setting to core hardening (Mar. – Apr.)
After the process of flowering has completed around mid-March, the leaves fully develop and reach their final size, while the first growing cycle begins with the vivacious elongation of the shoots. The fruit start to grow in late march, and at the same time there is increased activity in the root system in order to cover the requirements of sprouting and fruiting.
From this time until mid-April is a period when mainly the enlargement of the seeds and the cores of the fruits takes place. In mid-April, the pit hardens, the growth rate of the fruits slows down, and the first wave of shedding is observed.
At this stage the trees have high requirements in nutrients and water. Their requirements in Nitrogen (N) are very high, and its absorption rate by the trees is maximized.
Phosphorus (Ρ), Boron (B), and Calcium (Ca) are required for fruit setting, the growth of young fruits, and the formation of the pit. The requirements in Potassium (Κ) progressively increase after flowering and escalate as vegetation and fruits grow.
Magnesium (Mg), Iron (Fe), and Zinc (Zn) increase the photosynthetic activity of the leaves, improve the supply of the fruits, and reduce shedding.
From fast fruit growth to ripeness (Apr. – May)
From the second half of April until early May, the size and weight of the fruits increases at a fast rate, and they reach 90% of their final size. Fruit ripeness follows, starting with the color changing and culminating near the end of May, when the fruits have acquired their organoleptic characteristics.
At this stage, the requirements of the trees in Nitrogen are lower (it negatively affects the quality and storability of the fruit) and their requirements in Potassium are increased, as it migrates from the leaves to the fruits and takes part in the production of storage substances for the following year.
Limited supply of Nitrogen combined with an adequate amount of Potassium increase the size, weight, color, and sugars of the fruits. Calcium improves their storability, and together with Boron they reduce tearing during ripening. Phosphorus is highly absorbable at this stage, increasing the weight, color, and binding power of the fruits, and significantly contributing to the differentiation of the flower buds for the production of the following year.
Post-harvest (Jun. – Nov.)
After the harvest, the shoots keep growing until early July, while the differentiation of the flower buds that will fruit the following year takes place at the same time. The nutrients formed migrate from the leaves to the trunk and roots in the form of carbohydrates and amino-acids. These substances are crucial to the onset of sprouting and flowering the following spring.
Irrigation, along with the supply of certain amount of Nitrogen, is a key process after the harvest for the growth of vegetation, differentiation of the buds, the smooth transition of the trees to the phase of dormancy, and robust growth and healthy fruiting the following year.