By George! - A Blog!

Sometime in early May, when you take a look at your fruit trees and feel happy about a large number of developing fruit, something dreadful happens. A lot of little fruit–maybe all of them in some instances– have left the tree and are lying on the ground.

Why did this happen? Commercial citrus growers in Yuma anticipate this annual event and call it “June Drop”, though it doesn’t necessarily strictly follow the calendar. Some put the blame on “electrically charged” winds and the groves quickly get a carpet of marbles all through them. Strong, gusty winds certainly coincide with this happening.

In Tucson, in addition to citrus trees, we get fruit drop on apricots, peaches, and persimmons with or without the effect of “electrically charged” winds and it’s interesting to speculate on the main cause. Here are a number of possible reasons for this alarming fruit drop.

First, it’s possible that the tree has produced too many fruit anyway and cannot maintain them, so it’s a natural discard. A good flowering and excellent pollination always gives too many fruit. Citrus trees especially, but other fruit trees too, often run into alternate bearing. Last year’s heavy crop exhausted the tree and it now needs a rest. After a year of rest it’s inclined to overdo it, and so we get fruit drop.

Young trees, planted in the last couple of years, do not have the stamina to carry a large crop and therefore can’t help but shed their fruit.

But there are forces of nature that influence our trees’ behaviour. First the strong, hot, dry winds of May. Then there’s a temperature change. They usually come together suddenly, in combination or singly, and stress our trees. If we don’t compensate with additional irrigation, something has to give. Another management factor is the use of fertilizer. If the soil is dry and the trees’ need for water is high and we apply fertilizer too heavily, something has to give. Any combination of these factors is sure to affect our trees’ ability to hang on to the fruit it has produced.

We can help to minimize fruit drop. Basically we need to support the trees steady spring growth and this is best done by making sure they always have plenty of water. Irrigate deeply with a steady routine instead of waiting for the soil to dry. Alternate dry soil and wet soil simply shocks the growth cycle. Remember too, that a large amount of fertilizer has the effect of drying out the soil, and it’s better to give two smaller applications at two different times instead of one big heaping helping. After grapefruit (for example) have reached the size of a big marble they are not likely to fall off and you can be a bit absent-minded about their care.

It’s a fact of nature that tree seeds germinate when the soil is at a suitable temperature. That is happening now in May and June. It is also a fact that trees propagate by seed and some of them are remarkably efficient at this. A third fact is that these numerous seeds find their way to places where they are not wanted. Then we call them weeds.

It’s the wind that blows them up against our walls and it’s the birds that give a scatter effect to our landscapes. The common offenders include Mexican Palo Verde, Mesquites, Cat-claw Acacia, and Rhus lancea, but there are more. Birds help to spread Mulberry trees and Mistletoes. Seeds that are spread naturally in these ways seem to have extra-long roots and enough energy to get them well established very quickly and effectively (from their point of view). Sometimes such volunteers appear in places where we can use them in our landscapes but mostly they arrive near walls of buildings and sidewalks, or places where we irrigate our planted trees and shrubs.

Be observant, recognize them for what they are, and pull them out before they get too settled in their, but not your, favorite spot.