Tangerines splitting and falling off tree
I live in northern California (near San Jose), and I have a mature semi-dwarf tangerine (or mandarin?) tree that produces a big crop every year. The tree is probably 30 years old. This year, starting in about mid-October, lots of small green and, more recently, semi-ripe tangerines are splitting; most of these then fall off the tree. This started happening well before a couple of recent nights when we had an hour or two of just-below-freezing weather (which did kill many of my impatiens). We've had a good amount of rain in the last few months, although I probably wasn't watering regularly enough during the summer, and I also wasn't fertilizing as often as I have in most other years. But my grapefruit tree isn't having this problem and has lots of healthy looking fruit on the tree that seem to be starting to ripen. My lemon tree rarely keeps the fruit on the tree long enough to even ripen fully, but the lemons don't split--they just fall off a little green. I've done a little research on what may cause citrus fruit in general or tangerines in particular to split while they're still on the tree but I haven't found a clear reason for the splitting, or, more importantly, any ideas for how to prevent further splitting. Does anyone out there have ideas about this? TIA for any replies.