Blackberries not developing

Dear Lynn

I wonder if you have any ideas on a problem that we have been having over the last few years with our blackberries. They have given stalwart service over many years - probably 20 or more - but recently we have found that - particularly later on in the season - an increasing number of the berries do not ripen all over. In some cases just a few "blobs" (don't know what they are called)  remain red, but sometimes it is half or more of the fruit. Have you come across this? And if so, do you know what causes it ? Any help you can offer will be much appreciated.  it is such a shame to have all those lovely berries spoilt like this.

Best wishes,

Dan (Rutland)


Dear Dan

I do know what you are talking about and have seen it myself!  I think the problem is due to inadequate pollination. The drupelets (your blobs!) only develop when the ovules are fertilised by bees.  We all know that there has been a problem with the decline in bees and wet springs & summers or even hot days (what are they!) can reduce the number of bee visits to the flower and hence reducing the quality of the fruit. 

Incomplete drupelet development can also be a symptom of exhausted reserves in the plant's roots, or a viral infection such as Raspberry bushy dwarf virus but I doubt this is the case as you do not have reduced yield and your fruit are not crumbly.

Annual pruning is beneficial too, in Stephanie's Kitchen Garden I pruned and tied in the horizontal branches in late autumn and we have many more flowers (and hence fruit) than last year.

You might be interested in our Beepol Bumblebee Lodge this has become very popular with customers wanting to increase the bee population in their gardens and is quite fascinating to watch.

Kind Regards

Lynn Burton
Horticultural Advisor / Kitchen Gardener