GARDENING TOO MUCH IRRIGATION COULD LEAD TO SPLIT ORANGES.

Byline: Joshua Siskin

Does your orange tree have split fruit?

If so, do not despair. You are not alone. The conditions that caused your oranges to split are causing oranges to split all over the Valley. While this fruit-splitting phenomenon is not entirely understood, irregular soil moisture is most often mentioned in an attempt to explain it.

Splits typically begin on the bottom tip of the fruit and proceed longitudinally toward the stem end. Usually, only a small percentage of the fruit on a tree at any given moment develop splits. Split fruit is perfectly edible as long as you pick it before fungi or insects find their way inside.

The best way to prevent fruit split of orange trees is through proper irrigation. Over-irrigation of orange trees - and all other citrus, for that matter - is common. Even in hot weather, citrus should not need to be watered more than once every other week. In a dry winter, such as we experienced until only recently, monthly irrigations should be adequate. When you do irrigate, water deeply by allowing a trickle of water to soak the root zone for 12 to 24 hours, depending on how quickly your soil drains.

Splits are occasioned by rapid growth of the fruit pulp at the expense of the peel. A sudden increase in water uptake by the tree, made possible by heavy irrigation after a dry spell, or by a sudden winter storm, could cause accelerated growth and expansion of the fruit pulp to where it splits the peel.

A healthy dose of fertilizer administered to a tree that has not seen fertilizer for many months could have a similar effect. Winter temperatures that are warmer than average tend to push fruit to grow faster than normal and may also contribute to splitting.

Some research has implicated potassium and/or calcium deficiencies as causes of fruit splitting. Potassium and calcium give strength not only to fruit peels but to stems, bark, leaf cuticles and other tough plant tissues.

This discussion on fruit split was occasioned by an e-mail received from Sherman Kanne of West Hills, who was concerned about his dwarf Valencia orange tree. The tree is 17 years old and has abundant fruit, but many of them are split. Splitting is most frequently encountered in Valencia and navel oranges, as compared to other citrus. Very thick-skinned citrus, such as grapefruit, is least likely to split.

Compost critters

Herb Nacke of Northridge wrote me about the fig beetles - those metallic green beetles that emerge from pupation when the weather warms - in his compost pile.

Fig beetles cluster on overripe fruit such as apricots and peaches but are not a threat to animals or people. However, fig beetle larvae, those big white grubs you find in the compost pile, have been known to feed on and cause some damage to the roots of young plants and trees.