Experts tackle readers’ garden questions.
Q: My blood orange tree has produced its best crop ever in quantity since it was planted nine years ago, but the size is disappointing. Few fruit are as large as in previous years. Fully half are about half size. Is this a question of fertilizer timing? Watering? Thinning? Pruning?
A. Ellison Rumsey, El Dorado Hills
Sacramento County Master Gardener Cathryn Rakich: The blood orange, famed for its striking “blood red” interior, is an exotic choice for the home gardener.
Blood orange trees (Citrus sinensis) thrive in temperate climates such as the Sacramento Valley, with its warm summers and mild winters, and do well as containers plants that can be moved to shelter or easily covered during evenings of low temperatures and frost.
Reduced fruit size can be attributed to several issues, including nutrient deficiency, water stress and pests.
Mineral deficiency usually appears first in leaf tissue, causing leaves to turn pale green to yellow, but will eventually affect fruit size, quality and yield. The most common deficiencies are nitrogen and zinc, followed by manganese and magnesium.
When and how to apply a nitrogen supplement will depend on the type of citrus, fertilizer and climate, so it is critical to read and carefully follow label directions. Foliar sprays (applying fertilizer directly to plant leaves) can correct zinc, iron and manganese deficiencies. Chelated formulations applied to the soil near the tree also are effective. Also note that citrus trees do not require a lot of added phosphorus, and excessive phosphorus fertilization can reduce fruit size.
Correct watering practices also are critical to developing good quality citrus. Under-watering can lead to water stress, which can produce smaller fruit. During the summer heat, citrus require approximately 4 to 6 inches of water per month. However, depending on the soil type and drainage, this amount may be divided up into several applications, keeping the soil moist but not too wet.
Pruning and thinning is not usually required to keep citrus productive or attractive.
For more information on growing citrus trees and managing pests, visit the University of California Master Gardener Program website at homeorchard.ucanr.edu.
Cathryn Rakich is a UC Cooperative Extension Master Gardener for Sacramento County.
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to firstname.lastname@example.org. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:
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