Grape is a hermaphrodite plant, so in this season, grape flowers will complete the process of self-pollination. After pollination, the grape flowers will eventually develop into fruit, and this process is called Fruit Set. Under ideal conditions, every grape flower has the opportunity to develop and bear fruit. Of course, this only happens under ideal conditions. In reality, not every flower can be successfully pollinated and then developed into grapes. If fewer flowers are successfully pollinated in a certain year, then after the fruit-setting period, the failed flowers will wither, and the number of grains on each bunch of grapes is less than the average. People call this situation fruit drop. Uneven maturity is another situation, that is, although the grapes are pollinated, the fruits are seedless or small.
Fruit drop (source: WordPress)
To put it simply and rudely, falling fruit is more like "stillbirth", while uneven maturity can be described as "stunting". So what are the reasons that lead to these two situations? Whether fruit drop or uneven maturity is related to whether the pollination process of grape flowers is smooth or not. If the temperature is below 15℃, the pollination process will be interrupted. And rainy, cloudy or cold weather will have a negative impact on the pollination process. Sometimes, premature or excessive Prunning, excessive soil fertility, or improper selection of rootstocks and cloned varieties will all cause fruit drop. The lack of boron will directly affect pollination and lead to uneven fruit ripening.
It is conceivable that fruit drop and uneven maturity will directly affect the wine production in that year. In addition to reducing production, the health of the fruit will be affected, and it is easy to be infected with germs at maturity. Although uneven ripening will also cause different degrees of ripening of the whole bunch of grapes, some growers will welcome this situation, because uneven ripening will limit the size of grape particles to a certain extent and make the wine grapes more concentrated. Some winemakers think that seedless glucose is high, which is beneficial to brewing sweet wine.
Fruit drop can't be completely avoided, but people will take some measures to prevent it or minimize the loss. In addition to controlling the temperature of the vineyard, grape farmers will also choose clonal varieties that are not prone to fruit drop for cultivation, or adjust the pruning strategy appropriately. Sometimes appropriate chemicals are sprayed to supplement the trace elements needed for the healthy growth of vines to prevent uneven ripening.