EasyBloom Forum

Last year my raspberries bloomed and then the flowers withered. Zero fruit last year. This happened throughout my 8' by 15' patch. This patch has produced abundant fruit in the past. Any idea what happened and remedy. Thanks, Dr. Y

Hey Dr. Y...I have a couple of thoughts of what may have happened. First off, raspberries are known to be thirsty. Although blackberries are slightly more drought resistant, raspberries require constantly moist soil. (Also, it's very important that the soil drains quickly. Soggy soil can end up killing raspberries). If your raspberry suffered a drought during floral development, then it is possible that your raspberry could suffer from global flower abortion. In other words, all the flowers on the plant will fall off at roughly the same time.

Another possibility is that your raspberry is getting too old to be extremely fruitful. I'm not 100% sure that this is the case however, since old age usually results in a general decrease in fruit production as opposed to global flower abortion, which it sounds like you had. Generally, canes older than 5-8 years will start to show a reduction in fruit production.

Pollination could also be a factor, but once again I do not think this to be the case. Raspberries are mostly self-fertile and do not require pollinators to produce fruit. Raspberries that lacked any pollinators (bees more often than not are the pollinators) will show a reduction in the amount of drupelets per "berry". Drupelet is the name for the individual fruits...there are many drupelets per "berry". There will also be an overall decrease in the number of "berries" produced.

Another issue may be pruning, however, this is complex. Different varieties of raspberries require different types of pruning. Generally, red and yellow summer-fruiting varieties should be pruned right after harvest, whereas purple varieties should be pinched in early summer before harvest. Pinching and pruning are different and result in different outcomes. Since I am not sure which variety of raspberry you have, I cannot truly give you good advice with this issue. I may be able to help you more if you know which variety of raspberry you are growing.

Plant nutrition may also be an issue. Plants can abort their flowers if there is a boron toxicity. As random as this may sound, it actually happens more often than one would think. Also, too much nitrogen can cause a drop in flower/fruit production, but once again, this would not be manifested in a drop off of the flowers.

Mildew can also cause floral abortion. By chance did you notice any gray fuzz on any of the leaves last season? If you did, my recommendation would be to increase the air flow through the foliage by doing some maintenance pruning. By pruning away some of the canes, you will promote better air flow through the canopy which in turn decreases the chance of fungi infection.

Finally temperature may also be an issue. There was an article in Scientia Horticulturae long ago that discusses flower abortion at different temperatures. Although the model plant for this paper was different from raspberry, it is known that rapid temperature shifts can cause havoc on flower production in plants. Generally this is not an issue since raspberries generally flower in late spring through summer, but if there was a sudden temperature shift in either direction (colder or hotter) you may have an issue.

Having said all this, my final advice comes from my first post on this issue. Raspberries do best with constantly moist soil that drains well. If your soil does not drain very well (there is consistently standing water after you water), then this may cause the issue. Also, standing water increases the humidity around your plant, which in turn increases the chance of fungal disease infection. Also, if there was a quick bout of water stress during the flower development, you could see the flower abortion. Basically, when it comes down to it, fruit production is a costly process. Flower abortion can be a result of many kinds of stress. By aborting the flowers, the plant will cut its losses before too much is invested in the next step (fruit production) when the plant is experiencing some type of environmental stress.

I hope this is helpful. I apologize for the long diatribe on anything that could've caused a fruit production reduction in your raspberry. There are many possibilities, but my money would be on soil status. Of course if you have any further questions, please ask. I will try to keep it shorter next time. :) Cheers...Dr. Robby