Question: I have a Washington navel orange that is about four or five years old. The fruit is splitting. What causes this?
Like so many fruit with a rather tough outer rind, this is usually due to irregular watering practices: too much, then not enough followed by too much, not enough, etc. As the skin of the fruit begins to thin as it matures, the swelling of the fruit due to excess water causes the fruit to enlarge and then split. This can happen on citrus, pomegranates and even tomatoes.
Applying wood mulch around the plants at least four inches deep should help considerably. The mulch helps keep the soil from wide fluctuations in soil moisture due to our climate. Be sure to keep the mulch away from the trunk of the tree for the first four to five years or it could rot the trunk. As it gets more mature, the mulch on the trunk is not a serious problem, provided that you aren’t watering daily.
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at firstname.lastname@example.org. Visit his blog at