I'm disappointed in the flavor of my navel oranges. No matter what fertilizer I use or the month I pick the fruit, it's not very sweet. What's wrong?
It's nothing you're doing wrong. Orange County was named in honor of the Valencia orange, not the navel orange.
Ripening primarily in winter and early spring, navels are better suited to California's inland valleys, where cool winter nights are followed by warm days. This cool-night, warm-day cycle is what is needed to pump sugars into the fruit. Navel oranges grow fine here and even fruit well, but they generally don't develop a very sweet flavor.