Gardening with Gary

Gardening Advice from an Expert

Orange Trees

Q. What is causing my oranges to split? I have been so unhappy with them this year.

A. Splitting in Navel oranges often occurs on green fruit between September and November. In some years, splitting may occur in Valencia oranges but it usually is less of a problem than in Navel oranges. Splitting is a long-standing problem in most areas where Navel oranges are grown. In some years, the percentage of split fruit is high; in other years it is low.

Splitting is not known to result from any single factor. Studies indicate that changes in weather including temperature, relative humidity and wind may have more effect on fruit splitting than anything else.

The amount of water in a citrus tree changes due to weather conditions and this causes the fruit to shrink and swell as water is lost or gained. If the water content changes too much or too rapidly the rind may split. Good cultural practices can help reduce fruit splitting but may not eliminate it completely. Proper irrigation of citrus is very important. A large area of soil around a tree should be watered since roots normally grow somewhat beyond the edge of the canopy. Wet the soil to a depth of at least 2 feet then allow it to become somewhat dry before irrigating again. Do not keep the soil constantly wet or allow it to become excessively dry. When trees are fertilized, apply the correct amount of plant food and water thoroughly after it is applied. If soil is dry, irrigate before trees are sprayed with insecticidal soap, horticultural oil or other pesticides and delay treatment if the weather is hot, windy or dry. Promptly control gophers that feed on tree roots and do not cut or damage roots.

Assistance: Western Gardener Assn., San Diego, CA.

In Summary:
Oranges, Splitting - Changes in the weather are usual cause. High humidity after dry period can trigger.