My Daisy mandarin has had a lot of splitting fruit due to the heavy rains we have had. I tried eating a few, but they were still a little too tart, so I tried making a juice drink--with a little sweetening it is not too bad.

Splitting is one of the known problems for Daisy, but it is clearly related to rains.

The seemingly spontaneous splitting that occurs in citrus fruits,
particularly in navel oranges, and some mandarins is discouraging. Splitting is an abiotic disorder, that is, it is a problem that cannot be attributed to any living organism, such as an insect or plant pathogen, but one that stems instead from environmental or cultural conditions. There is no chemical control for this physiological condition. The split usually starts at the stylar end of the fruit, which is the weakest point in the rind. Splits probably occur when water and sugar are transported from the roots of the tree to the ripening fruit, and the rind is unable to expand quickly enough to accommodate the added volume. The rind burst open under the pressure. Some citrus varieties,especially thin skinned ones, may be more likely to split than other varieties. Rinds that have been sunburned or otherwise damaged may be less elastic than normal and therefore more apt to split. Although the exact cause is unknown, fruit splitting is likely the result of stress to the tree. Splitting appears to be most closely related to extreme fluctuation in temperature, humidity, soil moisture, and possibly fertilizer levels, and the disorder is probably caused by a combination of these factors rather than by a single cause. For example, when hot weather is combined with high winds, the tree becomes drought stress and begins to take water from the fruit, causing the fruit to soften causing it to crack. Young trees or dwarf varieties with relatively small or shallow root systems, as well as trees grown in very sandy or porous soils that do not retain moisture well, may be more susceptible. to fruit splitting. Reasonable cultural practices to avoid extreme fluctuations in soil moisture and fertilization levels throughout the growing season may help to minimize fruit split. Trees should be irrigated regularly to assure acontinuous supply of soil moisture, especially during hot or windy weather. When hot winds are anticipated, irrigate before the winds begin. After the hot winds subside, irrigate lightly for a few days and then resume a normal irrigation schedule. Instead of a single large application of quick release fertilizer each year, smaller monthly applications throughout the growing season may help keep nutrient levels constant. Timed release fertilizers offer the convenience of supplying nutrients at an even rate over the length of the growing season, but they are usually more expensive than other fertilizers. Split oranges are edible, although they are usually not ripe enough to be usable; they break down quickly and eventually drop from the tree. Damaged fruit should be removed and discarded, since they are susceptible to invading organisms that may cause disease such as Alternia Rot. Decaying fruit may also harbor fungi, bacteria, insects or other unwanted pests. - Millet (1.197-)

Not much I can do about the rains--over 5 ft so far this yr. I am just glad I can get some use from them by juicing and adding sugar. There were no split fruit last yr with our typical dry fall. Sept and Oct are usually our drier months (unless we get a hurricane).

The best to you and your tree. My guess is that your "soil" is mostly sand? Take care. - Millet (1,197-)

Our average annual rainfall is about 68 inches--but we are close to that already. The difference between here and the PNW is that we get rain in much higher doses--a 6 inch rain is not uncommon--even 12 to 15 inches in 24 hours happens every few yrs. We ahve even had rainfall events of 40 inches in a few days.

Even with our high rainfall, I have had to run the sprinkler a good bit --earlier this summer. Our sandy soil does not hold water more than a few days.

A few years ago I was talking to a professor from UC Davis, who asked me what kind of soil did I have. I said it was blasphemy to call it soil, as it was almost 100% sand. He wanted to know the organic content and I said nematodes.

My citrus trees planted in my old garden area, with 20 years of compost added, are twice as tall and have twice as thick trunks, and many more fruit, than the trees planted in the back yard in the sand. I don't know how much rain we have had this year, but a whole lot for sure.

"Soil" is pretty much the same here--pure sand--if you dig down a foot or more you may get a little yellow color in the sand--otherwise, it is just dirty beach sand.

I have some very productive trees, but they get monthly fertilizer from Feb to the first of Sept. and I add trace mineral mix annually.