Deciduous fruit trees such as apple, pear, peach and plum undergo a series of distinct stages during the annual cycle of fruit production. Although specific stages vary, depending on the type of tree, most fruit trees follow a similar pattern of growth and development. Fruit growers use these stages to evaluate the progress of their crop and determine when to prune and apply pesticides and fungicides.
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In autumn, deciduous fruit trees lose their leaves and store energy in the trunk and roots to sustain them during winter dormancy. Tiny, developing buds become inactive in preparation for winter survival. Dormancy prevents buds from opening prematurely during brief warm spells. Fruit trees require a certain number of chill hours, hours when temperatures remain between 0 to 7.22 degrees Celsius, to achieve optimal fruit production. Chill requirements vary, depending on the variety of tree. Correct pruning during dormancy produces vigorous spring growth; however, heavy pruning causes excessive growth of leaves and stems but little fruit production. Pruning too early in the winter makes trees more susceptible to winter injury. Application of oil-based pesticide and fungicide sprays during dormancy deters problems before new growth begins.
The swelling of flower buds in early spring initiates the budding stage. Buds that have received the correct number of chill hours emerge from dormancy, ready to begin growing when temperatures warm in springtime. Insufficient chill hour accumulation leads to delayed growth and reduced fruit production. Budding occurs in as many as 13 distinct phases or stages. The exact number and name for each budding stage is controversial and varies by type of tree. Typical budding stages include swollen bud, bud burst, green tip, tight cluster and pink or white bud. Knowledge of these stages helps a grower determine whether her crop has been injured by cold weather or is progressing normally.
Blossoming begins with the opening of the first flower buds and lasts until the petal-fall stage, when about 75 per cent of blossoms have fallen from the tree. During this stage, delicate blooms are particularly susceptible to damage from late spring frosts. Pollination is crucial during blossoming to ensure optimal production of well-formed fruit. Most fruit trees rely on insects such as honey bees to transfer pollen from the male to the female flower parts. Avoid using insecticides during the blossom stage to prevent killing beneficial pollinator insects. Full bloom occurs when approximately 80 per cent of a tree's flower buds are opened.
Fruit Set and Development
Depending on the type of tree, fruit set typically occurs sometime between March and May, about 4 to 10 days after blossoms appear. In stone fruits such as peaches, cherries and plums, the outer shuck splits away from the base, exposing the small, developing fruit. Fruit ripens over the summer months until harvest time, typically about 60 to 150 days after blooming. Hand-thinning the crop produces larger, better-formed fruit and deters breakage of tree limbs. During the fruit development stage, growers often apply chemical treatments to prevent and control pests and diseases to achieve blemish-free, marketable produce.
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- Cornell University; New York's Food and Life Sciences Bulletin; Growth Stages in Fruit Trees -- From Dormant to Fruit Set; P. J. Chapman, et al.; February 1976
- North Carolina State University Cooperative Extension: Training & Pruning Fruit Trees
- Oklahoma State University Cooperative Extension; Home Tree Fruit Production and Pest Management; Phillip Mulder, et al.
- Colorado State University Extension; Evaluating Tree Fruit Bud & Fruit Damage From Cold; H. J. Larsen; August 2010
- Texas A & M University; Chilling Accumulation: Its Importance and Estimation; David H. Byrne, et al.