In the Garden:
Northern California Coastal & Inland Valleys
July, 2012
Regional Report

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Sometimes citrus needs a little help.

Where Are My Oranges?

For the past few years I have been seeing a handsome young doctor for a vision problem. He, in turn, avails himself of my expertise to help with a problem he has with his citrus trees. Two trees are planted in his urban San Francisco backyard. One tree produces an abundant crop of naval oranges, while the other tree does not. They were bought at the same time, are the same variety, and are planted in the same general area of the yard against a south-facing fence line.

Don't you just love a mystery?

During the time I have been treated by this fine doctor, we have tried different things to encourage the barren tree to produce -- switching to a citrus-specific fertilizer, then increasing the dosage, hand pollinating, mulching and even going so far as to smack the trunk smartly with a baseball bat.

Allow me to explain...

Feed Me, Seymour!
First of all, citrus trees are heavy feeders. They also need a continuous source of nutrients, so slow-release fertilizer spikes formulated specifically for fruit and citrus trees are a good option. When the slow release spike brought no improvement, I suggested increasing the amount of fertilizer; however, there was still no fruit.
All of these conversations were taking place over a period of months, between my medical appointments, so I was able to evaluate the results of each method of correction we tried. Meanwhile, the doctor told me that the other tree was blooming, fruiting, and growing happily.

A few months later, the good doctor he told me that his tree was now producing flowers, but still no fruit. I crossed the lack of pollinators off my list because the other tree was performing so well. Sometimes, if there are no pollinators you can hand pollinate by using a small paint brush. Dabbing the brush from flower to flower will spread the pollen, in the same way a honey bee does as it goes from blossom to blossom. The fact that the tree was blooming but still not producing fruit suggested to me that improper watering could possibly be the cause of the problem.

What's a Guy Gotta' Do to Get a Drink?
Citrus trees need their roots to be constantly moist. Not wet, but just about as damp as a wrung-out sponge. Keeping the soil moist is easy if you put down a 4 - 6 inch layer of mulch. In questioning the doctor, I found that the non-bearing tree was near a concrete patio. That explained why the two trees had different watering requirements. Concrete absorbs heat, causing moisture to evaporate more quickly. Drying between watering will result in bud drop, so even if the tree was flowering, the fruit didn't have a chance to develop because of a lack of moisture. I suggested that my dear doctor increase the amount of water he gives his problem tree. I'll let you know how this solution works when I see him again in September...

Oh, by the way, using a baseball bat to smack the trunk will sometimes shock a tree into thinking it is under attack, thus causing it to produce fruit as a last-ditch survival instinct, or so they say...

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