Soon after flowering and fertilization occurs, the fruit starts to grow.
However, flowers in which fertilization did not occur, soon fall and many developing fruits abscise. Most abscission occurs within the first 4-6 weeks of growth, culminating in the so-called “June” drop. In the picture, fruit reaches around 30mm of diameter, and is surrounded by tiny undevelopped fruits which will fall.
The “King” flowers set better than the lateral ones. Also varieties differ a lot in fruit set. All these variables are influenced by weather, and locations (sunlight).
During the first 3-4 weeks of growth, both cell division and cell expansion are occurring in the apple. After this period, increase of the fruit size is almost entirely the result of cell expansion, only in the skin the cell division continues.
(source: “Apples – botany, production and uses”, edited by Ferree & Warrington, CABI Publishing)
Different varieties not only set and grow differently, also the colour of little fruits is different. Even in the same variety, the newest Galas are fully red in young age, comparable to the deep red colour typical for red-fleshed varieties.