The apple tree is a perennial plant whose life cycle repeats annually, moving through periods of growth and rest. This rhythm is finely tuned to seasonal changes, ensuring the tree’s survival through winter and optimal fruit production during warmer months. The process of an apple “starting to grow” is not a single event but a complex biological sequence. This journey involves several distinct, sequential stages, each dependent on specific environmental cues.
Preparing for Growth: The Role of Dormancy and Chilling Hours
Before visible spring growth occurs, the apple tree must satisfy an internal requirement called dormancy. Dormancy is a protective state entered in the fall, which prevents flower and leaf buds from prematurely swelling during winter warm spells. Breaking this rest period relies on the accumulation of “chilling hours.”
Chilling hours are the cumulative time the buds are exposed to cold temperatures, typically between 32°F and 45°F (0°C to 7°C). Most apple varieties require 800 to 1,750 chilling hours for this physiological preparation. Once the required cold is met, internal growth inhibitors break down. The buds are then primed to respond instantly to rising spring temperatures, dictating the tree’s readiness for the next growth cycle.
The Beginning of Growth: From Bud Break to Fruit Set
The first visible sign of growth is bud break, often called the green tip stage. This occurs when the swollen, dormant buds burst open, revealing green tissue within the protective scales. Growth then progresses rapidly through the tight cluster stage, where multiple flower buds are visible and grouped closely together.
The next stage is the pink stage, where individual blossoms separate and display a pink hue before opening. This leads into the bloom period, where flowers fully open, presenting the reproductive structures for fruit development. Successful pollination is required next, typically carried out by bees, transferring pollen to the stigma.
The apple fruit starts growing at fruit set, which follows successful fertilization. After the ovule is fertilized, the flower’s petals fall away, and the ovary begins to swell. This forms a tiny, pea-sized green fruit. This transformation marks the true initiation of the apple, transitioning from floral potential to actual fruit production.
The Stages of Apple Maturation
After fruit set, the young apple enters a growth phase lasting several months. Initial development is characterized by rapid cell division, which sets the foundation for the apple’s final size. This period requires consistent water and nutrient availability.
Once cell division slows, the apple’s growth shifts into cell enlargement. During this stage, the cells inside the fruit expand significantly, causing the apple to swell and accumulate water. Concurrent with this physical expansion, chemical maturation begins. Starches convert into sugars, and aromatic compounds develop to give the apple its flavor.
The time required for maturation varies significantly by cultivar, ranging from 100 to 200 days from bloom to harvest. Early-season varieties mature faster than late-season varieties, which may require 180 days or more. Indicators of ripeness include a change in skin color and the ease with which the fruit separates from the branch.
How Environmental Factors Affect the Timeline
The exact timing of growth stages depends on local and annual environmental conditions. Bud break and flowering are determined by the accumulation of growing degree days—a measure of heat units above a base temperature. A warm spring can accelerate this process, causing flowering to occur earlier than normal.
An early bloom increases the risk of damage from a late spring frost, which can destroy blossoms or newly set fruit. Summer temperature extremes also influence maturation. For example, hot days above 93°F can cause sunburn on the fruit. Warm nights, often above 59°F, can negatively affect the development of red color and overall quality. These variations mean the calendar-based timeline for apple growth is constantly adjusted by nature.