Why are my mature highbush blueberry plants not producing berries?
Question:
I have mature highbush blueberry plants. This year there is FAR fewer berries than in the previous 26 years. I’ve also noticed that several berries (but not all) are dying before they ripen. This seems to happen when they are still white, before turning purple.
Answer:
I’m sorry to hear the blueberries aren’t producing as well as before.
There are a couple of things I would consider first when faced with poor fruit set: lack of pollinators and pruning practices. Blueberries are pollinated by both bumblebees and honey bees, and if you don’t have enough of them around your plants, you won’t get proper pollination. This would be a likely culprit if you noticed the same number of flowers this year, but poor fruit set. Pruning is also very important for blueberries, especially as they age, and if it isn’t done properly the plants can become overgrown with old canes and fruit productivity will suffer. This can be remedied by renovating the plants with proper pruning at the end of next winter–i.e., removing the oldest canes each year at the base and keeping only the strongest shoots encourages vigorous growth of new, fruitful stem tissue from the crown.
If you didn’t see the normal amount of blooming this year, we would then think about the possibility of late winter/early spring frost damage on flower buds. It’s worth considering having your soil tested, too, though the UMaine Analytical Soil Lab in order to rule out soil impediments like deficiencies of key nutrients or problems with pH, both of which can interfere with fruit set. As I’m sure you know, blueberries prefer quite acidic soil and if the pH creeps too high, it will definitely impact the plant’s health and productivity.
If none of these seems applicable and you notice other symptoms besides the lack of fruit, I would need to see pictures of the problem areas and would probably recommend submitting photos/samples to the UMaine Plant Disease Diagnostic Lab. There is a small fee for their service, but you would get a confirmed diagnosis. But I’m hopeful the above advice may put you on a new path without the need for lab testing, and at the moment it doesn’t sound like there is anything to really submit as a sample (since the primary problems is the *lack* of something, rather than the *presence*).
As a final note, because you mention berries dying before ripening, I will point you to the Penn State Univ Extension’s page on mummy berry in blueberries–this is a somewhat common disease of blueberries. It doesn’t sound like it really matches what you’re seeing, but it would be good for you to read up on it and check the plants for relevant symptoms, to be on the safe side.
Happy gardening.