We grow a number of sweet and acid cherries at Rosemoor. Every year we have a fantastic show of blossom on the sweet cherry ‘Sunburst’, which is a fan trained tree on the wall in the veg garden, but every year just as the young cherries are forming they all fall off – very frustrating.
The problem first becomes noticeable when the fruit stalks start to droop and hang down and then within a few days all the fruit drops off.
There are a number of causes for cherries dropping their fruit, such as lack of water the previous summer, poor weather conditions at pollination time, either too windy for insects to fly or temperature too low for the pollen tube to develop properly.
However, none of these seemed to fit our situation exactly, but I recently learnt from an article in the Horticultural Week magazine that cherry growers in Kent are grubbing out their old cherry trees and replacing them with trees grafted onto a new rootstock called Gisela 5.
The normal rootstock used for cherries is Colt, which is semi-vigorous and apparently has a tendency to drop the fruit if the conditions are not just right at “stoning”, especially on exposed sites. Gisela 5 does not have this problem and is the first truly dwarfing rootstock. It has been used for a number of years in commercial orchards on the continent and has proved a good all round rootstock for sweet cherries.
Garry Preston, Fruit and Veg Gardener