I live in Toronto. Have had blackcurrant bushes in my garden for years. I never get any fruit from them: they flower, form tiny berries, and then they all drop off before they ripen. What do they need to turn into edible currants?
Hello – The Ontario Ministry of Agriculture, Food and Rural Affairs has a good factsheet on growing currants. I’ve included a link to the factsheet below. While it doesn’t specifically address the issue you mention, a couple of things stood out for me when I reviewed the factsheet.
First of all, it points out the need for regular watering suggesting that trickle irrigation is essential for currants. As black currants are maturing in the heat of the summer, are your plants receiving adequate moisture during this period? The plants may drop the fruit under moisture stress.
Secondly, black currants produce the best fruit on one-year-old wood. Are your plants being pruned regularly? Your currants should be pruned in the late winter or spring, removing all shoots that are more than 3 years old.
I hope these points or other information in the factsheet will lead to a bumper crop of black currants this year.