Q: I have a mature grapefruit tree I have been maintaining for three years ago. I keep it watered, fertilized and trimmed. It has always given me many wonderful juicy pink grapefruit, which I love, and share with friends. This spring, I noticed very few blossoms and now there are very few (probably less than 50 total) grapefruit on the tree. The existing fruit has extremely thick rinds, about 1ƒ inches thick, leaving very little room for the inside fruit. Did I do something wrong to have this problem? I love this tree and the fruit and would appreciate any help you can give me to do whatever it takes to bring back the bounty come next spring.
A: I recommend you double-check the fertilizer amount, timing, and type you are supplying. Over time, trees with an imbalance of nutrients may develop thick rinds. Nitrogen is often the main ingredient in fertilizer but trees also need a small amount of phosphorus and potassium. There are some fertilizers designed and sold for citrus. If you aren’t already using one of these, it might be worth switching. You also might also double-check the watering schedule to make sure that is correct. It should be every 14 to 21 days to a depth of 36 inches in the winter, every 10 to 14 days in the spring and fall, and every seven to 10 days in the summer. Trimming your citrus tree is not something recommended unless there are dead or damaged branches.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to firstname.lastname@example.org