What causes citrus fruit to turn green again (regreening)?

During citrus production, a phenomenon known as regreening can occur, which seriously affects the appearance of the fruit. It also causes both the sugar content and acidity of the fruit to decline, reducing fruit quality and affecting profits. So what causes citrus regreening? Let's take a look at the detailed explanation below.

1. Excessive nitrogen accumulation

Applying too much nitrogen fertilizer during the growing period causes nitrogen to accumulate excessively in the soil. Combined with rainy weather during the fruit ripening stage, this can very easily cause the fruit to regreen. Therefore, when the autumn shoots emerge, it is recommended to apply less slow-release fertilizer and instead choose quick-acting fertilizer as a shoot-promoting fertilizer. This can prevent fertilizer from not being fully decomposed and causing nitrogen to volatilize during cloudy and rainy weather, which would lead to regreening.

2. Weather and temperature differences

During the color-change period of citrus, low temperatures help the fruit accumulate sugar, anthocyanins and carotenoids, thereby promoting color change. However, if warm weather returns during the color-change period, the peel that has not yet fully ripened will regain its ability to synthesize chlorophyll, causing regreening. So once cold air or warm currents appear during the color-change period, it will either prolong the color change or cause regreening. Preventive measures should be taken during the color-change period.

3. Too much quick-acting fertilizer

If too much quick-acting fertilizer or foliar fertilizer with high nitrogen content is sprayed during the color-change period of citrus, the excess nitrogen will combine with the ventilation in the fruit to form organic nitrogen. This will reduce the sugar content in the fruit and cause the branches and leaves of the plant to grow excessively, competing with the fruit for ventilation, which leads to a decline in the sweetness of the citrus fruit and also a decline in the anthocyanin and carotenoid content in the peel. At this point, regreening is very likely to occur. Therefore, during the fruit color-change period, pay attention to the amount of fertilizer applied; do not apply too much quick-acting fertilizer, and also pay attention to the nitrogen content when spraying foliar fertilizer.

4. Poor tree vigor

For plantings with many fruits and few leaves, the nutrients synthesized through photosynthesis are limited, and the tree vigor is poor. The nutrients absorbed by the root system are also limited, so the fruit will change color early and show a false-ripening phenomenon. When fertilizer is later applied to maintain nutrition, the fruit will show a brief period of regreening. Therefore, for plants with poor tree vigor, promptly thin flowers and fruits to control the number of fruits set, and at the same time strengthen nutritional supplementation during the flowering and fruiting periods.

The above is an introduction to what causes citrus regreening. We hope it helps you. If you want to learn more related knowledge, please stay tuned to us.