Q: I have one grapefruit tree and one lemon tree age 25 years and one orange tree aged 6 years. Since the freeze of 2013, I have covered the trees at each and every frost. In 2014, the grapefruit yield was about 120, the lemons only 10 or 12 and the orange zero. In 2015, the grapefruit was greater, about 150, the lemon 100 and the orange three. In 2016, the grapefruit yield was 150, the lemon 150-200 (large sized) and the orange seven. This fall, the yield looks poor; grapefruit 25, lemon 100 (small) and no oranges. The trees are healthy, with good new growth. I water and fertilize regularly. Why the low yield? Also, when is the best time to prune the trees?
A:Β From your description, everything should be fine, so I am interested to know your irrigation and fertilization schedule and amounts in case they might be tweaked to help improve performance. The recommendation for watering is every seven to 10 days in the summer to a depth of 36 inches. In the spring and fall, watering should be done every 10 to 14 days and in the winter, every 14 to 21 days. Fertilization is recommended three times per year. The amount of fertilizer is based on the tree size and age, and the timing varies slightly based on the type of citrus. I recommend the publication that describes this because a graph is sometimes worth 1,000 words and I donβt have that much space. Google AZ1671 βCitrus Fertilization Chart for Arizona.β In the latest analysis, the oranges and grapefruits are fertilized on a different schedule from the lemons and limes, as you will see from the publication. In general, pruning is something that isnβt recommended for citrus trees unless there are dead, damaged or structurally unsound branches. In those cases, you can prune anytime the saw is sharp.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona.Β Questions and photosΒ may be emailed toΒ tucsongardensage@gmail.com
