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Index : Citrus and Other Fruits
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- 5. Many Factors Effect Citrus Fruit Quality - Top
- Citrus trees will be blooming shortly, followed closely on by the formation of small pea-size citrus fruits. As these fruits grow and develop over the spring and summer, certain aspects of care given to the tree can enhance the sweetness, quality and number of fruit.
At this time of year it’s important to fertilize citrus to supply an adequate level of nutrients for the development of healthy growth and fruit formation. Nitrogen is the most important nutrient to be supplied. Ammonium sulfate (21-0-0) has 21% nitrogen and is the standard citrus fertilizer used in Arizona. However, from time to time it’s good to add phosphorous to the mix. Ammonium phosphate (16-20-0) has both nitrogen and phosphorous and can be used for one or all of the recommended three yearly fertilizations. Unlike nitrogen, phosphorous must be scratched into the top half-inch or so of soil to be absorbed by the roots.
A word of caution about fertilizing citrus - don’t overdo it! Too much fertilizer, in particular - nitrogen, can adversely effect the quality of fruit. In fact, grapefruit should be fertilized with only half the amount recommended for other types of citrus. Too much nitrogen, and the rind of grapefruit will become excessively thick!
If your citrus tree has dark green leaves and adequate growth, you can lighten up on the amount of fertilizer applied, or skip one of the three (February, May, September) recommended
fertilizations all together.
Because of our prolonged warm winter weather, flowering has already begun on many trees and may coincide with the recommended February fertilization. Contrary to popular belief, fertilizing citrus trees during flowering or early fruit set does not adversely effect blooming or fruit development.
Adequate watering is probably the most critical aspect in the development of quality fruit. Fruit that’s dry on the inside with dry pulp is a frequent complaint of backyard citrus growers. It’s most often caused by lack of sufficient water when the fruit is developing. Fruit cracking is also related to watering problems. The outer rind can spit open when the tree is lacking water and is then give lots of water, either by irrigation or rainfall. The sudden swelling of the fruit can split the outer rind. If watering is consistent, splitting is less likely to occur.
Watering should be increased at the time citrus begin flowering. In fact, from the onset of blossoming to the time fruit are quarter-size in diameter, extra water should be supplied. Where as the recommended watering would normally be one time per week, increasing to twice weekly during this period should lessen fruit drop and improve fruit quality. If you have sandy, well-drained soil it may be necessary to water three times weekly - but with a smaller amount per application.
Deep watering is the key to success. If you’re irrigating with drip, run the emitters long enough to soak the water down 2 to 3 feet deep. This may take several hours. If you only have two or three emitters per tree add more emitters or use a soaker hose to supplement your normal watering.
If adequate water is applied to the tree(s) during the growing season, then fruit should develop properly. The sugar content of the fruit will depend on the stage of ripening. To have an appealing taste, the fruit must have a balance between these sugars and acids. Too much acid and the fruit is bitter. Too much sugar and the fruit is bland and tasteless. Of course, tart lemons and limes will have a much higher acid content than oranges and mandarins.
The variety of citrus will determine it’s ripening range. For instance, Valencia is a late ripening variety of orange that is at peak quality sometime between mid-January and mid-March. Most citrus fruit, such as Valencia, should be tested weekly for taste during it’s ripening range. When the fruit tastes good, it’s ready for picking. The exception is grapefruit. Although grapefruit may be picked as early as December, the sweetness and quality will continue to improve into early spring.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: February 20, 2005
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