Q: You recently provided some info on fertilizing citrus and I have located the chart you referenced. You often recommend watering to a depth of 36 inches, so I’ve been using a deep watering rod on my three mature fruit trees (10-12 feet, grapefruit, lemon, and orange). What is the preferred method for applying fertilizer? Should I use a pre-mixer with the watering rod below grade or apply the fertilizer on the surrounding ground under the tree and soak it from the top down?
A: The preferred method of fertilization is to spread it around the drip line of the tree and water it into the soil as you described. This is also the preferred method for irrigation so you can do both at the same time. I don’t recommend the deep watering rod because it likely bypasses some or many of the absorbing roots of the tree, which are typically in the top 1 to 2 feet of soil.
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Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
