Cherries are a stone fruit whose production results from a specific biological process on a specialized plant structure. The journey of a cherry from a tiny bud to a ripe fruit is a complex cycle dependent on precise botanical and environmental conditions. This exploration details the type of tree that produces this fruit, the climate required for its growth, and the annual biological sequence that ensures a successful harvest.
Classification of Cherry Trees
Cherries belong to the extensive Prunus genus, which includes deciduous trees and shrubs like peaches, plums, and almonds. Two primary species account for the vast majority of commercially grown cherries. The sweet cherry, most often consumed fresh, is Prunus avium. Conversely, the sour or tart cherry, typically used for cooking and preserves, is classified as Prunus cerasus.
Sweet cherry trees are relatively large, reaching heights of 15 to 30 feet in cultivation. These trees are characterized by a strong central trunk and often display a symmetrical conical crown when young. The fruit is a fleshy drupe, consisting of a soft, pulpy exterior surrounding a single, large, hardened pit.
Cherries primarily develop on specialized, short branches called fruit spurs, rather than directly on new growth. These spurs are robust structures attached to older wood that remain productive for many years, sometimes for 10 to 12 years. This fruiting habit means the tree’s older branches are the most productive parts, necessitating a different pruning approach than trees that fruit on one-year-old wood. Sour cherry trees also rely heavily on these spurs.
Essential Environmental Requirements
Cherry trees require a specific period of cold temperatures during the winter to break dormancy and flower in the spring. This necessary period is quantified as “chill hours,” defined as the total number of hours the dormant tree is exposed to temperatures below 45 degrees Fahrenheit (7 degrees Celsius). Sweet cherry varieties often require 700 to 800 chill hours annually. Sour cherries generally need over 1,200 hours of cold exposure to ensure uniform bud break.
Insufficient chill hours lead to poor yields, resulting in delayed leaf and flower development and an uneven bloom period that complicates harvesting. Cherry trees also require full sun exposure to thrive and produce high-quality fruit. The preferred soil type is moisture-retentive but must have excellent drainage, as the trees will not tolerate wet or waterlogged conditions.
Another environmental factor is the risk of frost, particularly during the early spring flowering stage. Cherry trees are among the first fruit trees to bloom, making their delicate flowers vulnerable to late cold snaps. The pistil, the female reproductive part that develops into the fruit, is the most susceptible to freezing temperatures. Temperatures dropping below 28 degrees Fahrenheit (-2.22 degrees Celsius) during the swollen bud or flowering stage can damage the pistil, leading to crop losses.
The Annual Fruiting Process
The annual cycle of cherry production begins when the tree emerges from winter dormancy, triggered by the completion of its necessary chill hours. Once the cold requirement is met, the tree prepares for flowering, with buds swelling and opening in early spring. The timing of this bloom is directly influenced by the preceding winter’s climate.
The small, white flowers that appear are hermaphroditic, containing both male and female reproductive organs. Successful fruit development relies on pollination, primarily carried out by insects, most notably honeybees and wild bees. Most sweet cherry varieties require cross-pollination, where pollen must be transferred from a compatible, genetically distinct cultivar. Without a suitable pollen donor planted nearby, these varieties will fail to set a sufficient crop.
Once the pollen lands on the flower’s stigma, a pollen tube begins to grow down toward the ovule for fertilization. This fertilization process is highly temperature-dependent, with optimal growth occurring between 59 and 72 degrees Fahrenheit (15 and 22 degrees Celsius). If the temperature is too low, the tube’s growth is slowed, and it may not reach the ovule before its viability window closes, resulting in a failed fruit set.
After successful fertilization of the ovule, the ovary within the flower begins to swell, marking the fruit set stage. The developing cherry moves through three distinct phases: cell division, followed by the hardening of the stone or pit, and rapid cell elongation that leads to the final fruit size. This development continues through late spring and early summer, culminating in the harvest of the mature, colored fruit.