- Fruit trees begin a dormant period when harmful conditions are ready to begin, such as in winter. Cooler weather, decreased rainfall or shorter days can trigger a suspension of growth until it is safe for the tree to restart its growing cycle. Dormancy is necessary for the health and life of fruit trees. A tree will not survive if it is taken from a location in which it has cycled through dormant winters to an indoor location where it gets light and heat throughout the following winter. Fruit trees need a period of rest and cold to bring on their growing cycle in the spring. Even orange and lemon trees must go through a dormant period in Florida and California. Their cooling cycle is much warmer (35 to 50 degrees) than what other fruit trees need in colder locations.
- Fruit trees, as well as other types of deciduous plants, begin preparation for dormancy through a change in their soft tissue (new growth). Fruit-tree leaves release a lot of water during photosynthesis (when the fruit tree turns sunlight into energy). When conditions change and the tree approaches dormancy, it ceases photosynthesis. The chlorophyll in the leaves breaks down, making sugars that go back into the fruit tree's limbs, trunk and roots. The location where the leaf joins the tree swells, blocking water to the leaf and causing it to die and fall off the fruit tree. Sugars stored in the tree help to lower the freezing point of the tree tissues.
- The roots are the first part of the fruit tree to become active, usually during late winter. New shoots and leaves are fed carbohydrates and water from the growing roots. A sugar-water solution moves through the tree to open buds and begin the fruit-growing process. The tree continues to feed the fruit the sugar-water combination throughout its harvest. That is why fruit ripened on the tree is so much sweeter than fruit that is picked green and allowed to ripen on its own.
