Orange, lemon, lime and grapefruit trees in the Citrus genus are native to tropical and subtropical regions of Asia and Australia. They can be grown in humid tropical and subtropical areas or in a Mediterranean climate, roughly in U.S. Department of Agriculture plant hardiness zones 9 to 11, depending on the variety. They grow best and yield the most fruit at daytime temperatures between 77 and 86 degrees Fahrenheit and typically stop growing at temperatures below 55 F. The age at which they bear fruit depends on the type of citrus, the weather and whether or not they receive proper fertilization.
Citrus Tree Flowering and Fruiting
Trees growing in tropical climates will grow blossoms and yield fruit off and on all year. The yield timing is different for trees growing in Mediterranean climates. More than 300 hours of accumulated temperature below 68 F will induce flowering and fruit production. This is called the chill factor. Large numbers of citrus flowers drop from the tree after they open and an equally large number of young fruits will drop from the tree.
Immature Tree Fruit Yields
Citrus trees usually grow little during the first year after they are planted. If they receive enough water and fertilizer, they grow substantially during the spring and summer between their second and fourth year. During this time, they may occasionally flower and yield fruit.
Mature Tree Yields
From the fifth year onward, citrus trees enter their fruit-bearing stage. When they begin bearing fruit, they grow more slowly, especially during the winter. They reach their full size 10 to 14 years after planting. After 20 to 25 years, the trees reach their peak production and their yield of fruit declines
Fertilizing to Encourage Fruit Yield
Citrus trees need to be fertilized to encourage flowering and fruiting as they mature. For the first year after planting, University of Arizona Cooperative Extension recommends applying 1/4 pound of actual nitrogen in three applications: once in January or February, once in April or May and once in August or September. For trees 2 to 4 years old, apply 1/2 pound of actual nitrogen three times, according to that schedule. For trees 3 to 4 years old, apply 3/4 pounds of actual nitrogen in three applications. For trees 5 to 6 years old and older, apply 1 1/4 pounds of actual nitrogen in three applications. Fertilizer numbers on a bag of fertilizer show the ratio by weight of nitrogen, phosphorus and potassium. To calculate the pounds of actual nitrogen in a particular fertilizer, multiply the weight of the bag by the percent of nitrogen. For example a 50 pound bag of 10-10-10 fertilizer contains 50 times 0.10, which equals 5 pounds of actual nitrogen.
Watering to Encourage Fruit Yield
Citrus tree yields drop when the trees are stressed by drought. Their roots extend about 1 1/2 times the spread of their branches. During dry weather, water this area every two to six weeks with enough water to wet the soil 3 feet deep. Depending on the soil, this usually requires 3 inches of water with each watering. Mulch helps retain soil moisture, but should not be placed near the trunk of a mature citrus tree.
- CultureSheet.org: Species Profiles for Pacific Island Agroforest: Citrus L.
- University of Florida IFAS Extension: Citrus Culture in the Home Landscape
- University of California Cooperative Extension: Growing Citrus in the Sierra Nevada Foothills
- University of California, Riverside: Questions and Answers to Citrus Management
- University of Arizona Cooperative Extension: Fertilizing Citrus Chart
- University of California Cooperative Extension: Citrus for the Home Garden
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