Keeping ‘June Drop’ at Bay for a Fruitful Citrus Harvest
Question: When my Valencia oranges become the size of a marble, they all drop off the tree. What is causing this, and how can I prevent it?
Answer: Citrus flowers generally form on new growth in late winter and early spring, though some may appear in fall. There are always many more flowers produced than eventual fruit.
Depending on the weather and available moisture, often less than 5% of fruit achieves maturity. The rest fall off, usually during the first high temperatures of late spring or early summer. This is known as “June drop” and is actually a self-regulating mechanism in citrus that ensures that trees don’t set too much fruit, which can be damaging.
Though some drop is to be expected, you can prevent losing too much fruit by properly watering and fertilizing your tree.
Without the appropriate water supply, you cannot expect satisfactory tree performance. More trees are stunted or lost by drought stress than from any other cause. To ensure adequate moisture, the soil should be thoroughly wet before wilting occurs.
Avoid overwatering, however, because this can also cause problems. It is critical that the area has good drainage. Water slowly, soaking the area well, so that the moisture reaches 4 feet. Then let the area dry some before watering again, because continuously saturated, airless soil encourages disease and can also cause fruit drop.
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Frequency of watering depends on the age of the tree and the weather. Young trees will need more frequent water than mature ones. Container trees need even more watering.
As for weather, hot and windy days will cause the plant to lose water quickly. Keep your orange tree healthy by fertilizing in late winter, June and August with a high-nitrogen citrus food that also contains iron.
Ask your local California Certified Nursery Professional (CCN Pro) for specific instructions on how much to fertilize your particular tree, or follow package directions.
Orange trees need very little pruning. Prune only dead or crossing branches or those that are creating a hazard.
If your watering and fertilizing practices are correct, check the tree for mites and scale. This can be done with a hand lens or by taking a piece into your local CCN Pro.
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Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or send e-mail to ucmastergardeners@yahoo.com. Calls and e-mail are picked up daily and are generally returned within two to three days.
